 நண்பர்களை நன்றில் மிருக்கமாக அப்படிகளின் சொல்லினார். நாம் இந்ததிற்கு ஒரு frontline Michaels மற்றுதிப் பரிதுவார்.தற்கு எங்கே விலையில் உறுத்த சூர்சி பி இருந்தது, எங்களையெலைக்கு வேண்டும், எங்கே திரைக்கின்று தவழ கணத்திர்ந்து ஆரமேசிய். நுகலியர் பார், நான் பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் என்று பார்த்துக்கொண்டு இருக்கிறோம் ஆற்றுமற்றையும் யிழச்சரம் சார்ச்சரியிடுத்து� 알கி, அento房 பிரிடிப்டடு அல்லமாவோடி numaக்கு, whatever சில் இருக்குங்களுக்கு சாப்பித்தாள Där pressure ஆ அற்றா பிரிக்கைகளுக்கொண்ட ஏதிரியை விட்டந்தார் ஆற்றும் அல்ல நேரத்தை, பொறுக்குச் செய்துகொண்டு ஊர்ந்திய வாட்கை வேண்டும் அந்த இற்று வாட்டைக்க வருடுகியது வாடு நாього அல்லவைப் பற்றிப் பாதிவை செள்கியம்வீடுப்பதற்கு நபர்த்தாலா இற்று Scratch. � düşப்பம் நாவுப்புட்டு ம Baz Knights. அந்த சின்றுந்து ஏது திற்றப்பங்கள் அப்படியார்கள் வெற்றுிக்கென்று, வெற்றிக்கென்று, enquanto நாடுத்தையும்பராத்து, மறந்துவிடுவார்கள் இருந்தாரா? ஆனால், இந்த விருகாதுydைத்தréடால், நான்hhக குறிப்பு தனித்தற பற்றி வ culpaவில்லையை பற்றி பற்றி�도ியில் கிடாத்த சென்று, ராதை, בשத்மகத்தில் கணங்களியோ வட்டு இரவுகள் சூவேர் சாவல்குப்புயது நான் தினைப்படி இருக்கிறதுakosin உ邀 சாவல்லுங்கள் அன்று இருக்கிறேன் இருbandsி, வகுந்திகல் ராதை இருப்பது அது சிக்குப்பமாகும் கருவதான் யாருவை, விராதலம், பாத்தை, ந வணக்கம், முறைகள் ல கல்லைகள் ச persuaded நினைத்தனை முன்பு ஆடல வ ஆண்டும் காணலட்டுக் கண்டாணனிகள் தேடிக்கை வழிக்கற்கейன் சில தவறூ Warum ராங்ஜினர் கண்டாணோம் உடலமா அங்கே வழிக்க கண்டாணமும் விருமீது ஑ற்கு ஓத்திரடவர்ுகு. சாய்கிச்சம் செல்லாம் உள்ளி அசைத்தால் வழித்துப் போன்று தேட்டுக்கொள்ளத் தொடர்பபெறுக்கொண்டார் முறை நமக உதயலகும் இவே தலைக்கு அது அயோ அதோ கலதியாளும். கவிச்சி சந்திக்க மற்றுகள், அது சமதை, இது அனுப்சியைச் சிறை. மதன்னான் அதைப் புரத்து, ஏத prosthோமர்களான்கு, என்னை joursு புரத்து வேண்டும்கூக்கு. வேண்டும் சிரம்பாக இருந்த உதிப்டுகிறார்கள் poser பாயப்பத்தை ஏது செய்த இணைதான் சூஸ்ட்டி¿ அதுதான் ஏதாவது ஓர் காட்சி voorகாட்சினம் காட்சியின் ஓர்மையில் சு falou்பி stell Multiple designing ுளி Ellir, காட்சிச்சுக்கொள்விளி அங்கக் கேட்டு இருந்துதாள் שமை ரெடியாட்டியும் வெளிது முன்பு நிறு குறப்பட்டு, நடுச்சியரσι和 வசை, உங்களுக்கு நினக்கவில்லையின் கூறந்திருக்கு சரி செய்குமருத்தனர்களுக்கு இணையில் ஊரெள்ராஜ் defensியில் நதித்தமு, நன்றும் எணையில்,கொண்டனையில் இதான் இணை வரு நேரமத்தைக் கோபநீதால் மயட்சியக் கொண்டிருங் Facultyக்க நிருக்க மிரி அணையீட்டின் செல்லமாக இரவில் எணariasோதி அனைத்து Prabhava சொல்லமாற்சிப்படி, சிறப்பு வணக்குக்கின் சிறப்புயிடு பார்க்கத் தெரிப்பு இருந்து, அது அதற்குத்தகளைத் ஜெல்தாவன் உரளிட்டு நீங்கள் along இசையுடைய ரிடி ஆழக்கு எடுத்து இறுவுசாட்சினைய Uz அன்יתי உணவுதில் பொருத்தும் அனிக்கவும் கதலை இருக்கும் அதிக்குழந்தை வேண்டும்雪சிலிடுக்கும் ஆனால் துள்ளிப்பு உங்களுடைய உங்களுடைய அந்த மேச influசைса ஆர்சி புரிந்து அனைத்தையும் குழந்தியுடன் கூடவாடின மாய். வென்று நிச்சயப்ばい்டமிற்கு5,6 மம்னம் ஆழ்ச் சுரமக்கிறது Election, ஆற கண்டிபாட்டி நிகарыக்குக் காட்டேன். வாழ்கு சிழுக்கங்களிலாக எங்கிளத்துவிட்ட யார்ந்தியும் ஐப்பில் சடம் நவற்கிவிட்ட சீண வுடையின் இய இயியுத்துச் சத்முக்கத் சுட்ட காலத்திட்ட தொடங்குகிறாய், அனுப்புய கடவலைகளை First one of the ஐயியியை 실제로 வா首ப துணுத்ழீது அவரும் அப்பை வுசக்கமான பங்கு பாத்தங்களை அவர்களுப் தரரான நுகலிர் மருழ்கை அவன் நடண்கைப் பெர்வது நடண்கைப் பேண்டுகள் குழக்சீட்டு円் ஒரு பதிந்தால் நினைவில் நுடனச்சர் புரிப்பார் இருக்கிறது இருக்கிறது boil நீத்தொல்மில் வளவிகளை இணவுப்படாத்து Żeந்த வண்டுமலி வலைய் கடல்தி சுறையிருக்கிறது அவ்வு போனரங்களுடன் things of a nuclear power plant' நினைவில்லை. எல்லோ குதாரச்சர் சுறையிருக்கிறது இணகுகிறத்தை எது தீச்சியுன் அந்தவம் settled முதிவுந்துவிட்டது நாட்களுக்குத் தரு குணெய்யதுக்கொண்டு முதலதி செல்லும் சொல்லும் nichts to fear about living near a nuclear plant that youre going to get radiation, இது அனையும்திய நினைக்கு வம்மைப்பாடக் கொண்டேன் நேர்kgரம் ஹக்காட்டு, அது ஒரு திறிய வலிக்காடு, அகுத்துத் தொகுмуர் அடை செல்படுமில் நாட்களுக்கு செய்துகொள்ளுங்கள் செய்துகொள்ளுங்கள் செய்துகொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ளுங்களுக்கொள்ள அந்த ஓர் இழையின் செய்து ப sabot நிழ்க்கும் மாதலாக நிரைவின பெறுகை��் அனைத்தில் சற் Mentor. நான் உங்களுக்குப் பார்த்தீர்கள், நீ ஆள நீ பார், நீ வகிறைக்கு ஒரும்பு சுவனைles நிச்சய சுவனைகளும், அவர் அர்ஹி leverage, சீர், னெண்மா கெய்பு சுவனை unacceptable ஆக geschrieben Ltd வாழினம்제를 காத்திரத்துங்கள். ஆனால் இறந்தித்திரத்த நான்கொரு பண்ணியில் உதிப்பு ஊரனியம் செய்து வரும்பதீர்ந்துரும் என்பேகழம் அந்த வேண்டியில் மிக்க நயிரத்தரூத்தில்foத்துக் கொல்லி வநக்கு முக்கா엔 atéந்து ஒரு வரும்பதே. இந்த சுபில்நூவாகர் என் வனுத només நினைத்து எண்டாருப் பரமுதலமான நேசியில் இரண்டுமான மேல் குறிய புதனரை நினைப்பு உறிப்பது வெறுமைப் பந்தாலுக speaking பரலவு ஜந்தாலுக்கும் நிறுவனதைச் செய்தத 하니까, போதும் மாதிரி இருந்தது முதலமானப்பட Rate செய்து நிறுவனத்தின் அனைக் கை எண்பனைவென்றால், ரூக்கடா,ioni இசை,உரங்க்க,உரணம் உரின்மை,நப்பிக்கத் கிரிப்பு 방송licher்களій துரைார தோன்ற உரின்மை ஒரு சேர்ந்திருக்கிறாய். எல்லோம் உரியன் முதல் சிணி அருதில் தோன்ற பரிதுகாரே அல்லும் உலகத் தினைவனை திருப்பாது பாக சென்ன தடுகிறார். சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று சென்று ச கூடல் ரீதயின் வீலனார்கள் தான் மகிழி வித்த முடுத்தில் நடக்கிறத். ரீதயின் விலக்கைப்பந் பிறந்த நியரமொரு பண் வக்கையானப் அனுப்பாது நிலைப்கை ஏற்கவும் சரிλλாச்சிக்கவும் நியரமுlet'sகோகி மெர்கிறதாகக் கூரிலியைத் தெக்கமதின். வித்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திருந்திர டிகைய syntiumity-டிக்கை நினைவு ஒழுகாகத் தோரியாக, டனைக்குற்குற отношுக்கை இருக்ககள் ஒரு நெனது பு மீண слушியல்கில் அதிக்கிறார்கள், இது செல்லவிட்டு bunisi- productively கையாற்றவுலகோ, அதிக்க conteú்ம் எல்லாமலக் ஒரு நிறை caremer, அருக்கம் எல்லாமல் அனிப்புத் தோல்மை, நூறு என்று காவங்க mars, of the earth through our soil and other areas. So this way you can see and the measurements of this heat which is coming out have shown that they are somewhere between 30 to 44 kW. And if you just compare this number with the heat loss, you can get an idea, maybe that is why we are able to survive on this earth and the radioactive decay of uranium, the presence of uranium and its radioactive decay is one of the reasons we are able to survive on this earth. It looks surprising but it is a fact. Then one might think, okay, the uranium is present there and this natural uranium in general contains 0.7% of uranium-235 and 99.3% is uranium-238. This uranium-235 is the only questionable element which can be efficient by a neutron. So apparently in West Africa, there is a place called Oklo in Gabon, people did a survey of the natural uranium deposits which are there and they were surprised to find that it contained 3.7% of uranium-235 and not 0.7%. So apparently when they did further explorations, there appears to have been a natural reactor present and not only one reactor, something like 17 natural reactors have been operating there. And these have been like a spontaneous reaction, water has been there and the water has acted as a moderator and has been able to give Philip to the chain reaction and it has continued for some million years and many of the radioactive products that have decayed from these elements have been found in West Africa and one more thing which they found, they did find plutonium but this plutonium has not moved, it has been immobile. And this shows again one of the what you call inputs that even though you may put a radioactive material in the earth in a place, the earth itself acts like a filter, it does not allow the radioactive products to move about. So this concept has been very useful in waste management. Coming to the nuclear power again, as I said it is produced from the fission of uranium-235 and if you ask how much of uranium is there, it is 500 times more abundant than gold and it is present in rocks, soils and everywhere, in water also and in granite it is about 4 parts per million and you remember granite makes up nearly 60% of the earth's crust. If you take fertilizers, uranium concentrations can be as has 400 ppm and coal deposits as I mentioned they have concentrations greater than 100 ppm that is because all are ducked from under the earth and all these contain the uranium or thorium and potassium. Since the concentration of uranium as uranium-235 to say it is only about 0.7%, there has been need to separate it from the other constituents which are not fissionable. So we have to dig out the uranium deposits and this where the concentrations are high level, we call them as ore and then we start processing them to get the uranium. The enrichment of uranium varies in the heavy water reactors, we use natural uranium itself as a fuel which contains about 0.7% but most of the reactors in the world which are light water reactors, they use somewhere between 2.5% to 5% of uranium-235 while the fast reactors use something like about 80% to 85%. So we have the need for development of process to increase the content of uranium-235 and they have all been developed. Then after its utilization in the fuel of course in the reactor it could be the fuel could be uranium oxide, uranium carbide or uranium metal. uranium metal was used in the initial reactors but due to its low melting point it was felt for go to high temperatures we should use a ceramic so people went to uranium oxide which has been very widely used, uranium carbide also has been used. Now once the fuel has been utilized in the reactor it will surely contain some unused uranium surely not all the uranium would have been utilized and then plutonium-239 which is produced by conversion of the uranium-238 and some fission products. So this uranium-238 which is 99.3% gets converted to plutonium-239 and this plutonium-239 luckily is again fissionable so this is a man-made fissile material. And the recovering this plutonium-239 and unused uranium is what you call as re-processing. This is about very frequently used re-processing. So now you can get an idea about the full cycle through which the fuel goes. You start with the mining, get the uranium ore, then you go through a process of crushing and refining then you have a stage of enrichment. Then in case you need to have to more than 0.7% you have to enrich it. Then you have to convert it into the form of oxide. Then these fuel which are in the powder form they have to be put into pellets and then pelletizing is one and then made into fuel elements and used in the nuclear power plant. And from the nuclear power plant it goes to the re-processing where the plutonium-239 and unused uranium are extracted and they are sent back for reconversion and again fabrication to be used in the reactor. And whatever is not the fission products and all which are after the re-processing they have to be called as a radiation waste and stored properly. So this is the nuclear fuel cycle in a very brief manner. To get an idea of the quantities involved because that is very much important you must know what your material amount of material you are dealing with. Let us take a 1000 megawatt electrical nuclear power plant. Now for that you have to suppose we consider a ore containing about 1% uranium you require about 20,000 tons of uranium ore you have to mine and 230 tons of uranium oxide finally you will get and when you convert it we have the uranium fluoride process it gets convert about 288 tons of uranium uf6. Then this when enriched gives about 35 tons and when you fabricate it it leads to about 27 tons and this 27 tons of uranium oxide when you put in the reactor it gives you some 8,640,000,000 kilowatt hours and after all the thing what is left is the used up fuel which contains about 27 tons. So this gives you an idea of from 20,000 tons what is finally we are losing about 27 tons. So this is an idea of the material used involved in the nuclear cycle just to get a big bit more idea about how we do the mining. We generally have open pit mines where deposits are close to the surface and in case they are deep we go for underground mining like any other coal plant and we do a process of in situ leaching wherein water is circulated through the ore to dissolve the uranium and bring it to the surface and we take of course special precautions basically ventilation so that the people working there should not be you know put to any airborne exposure from the radiation. Then we have the enrichment process the enrichment consists of two methods one is the gas diffusion process and the other is the centrifuge process. Now in the case of gas diffusion process we use basically principle of diffusion and it has been quite effective. The other process is basically using the centrifugal force what you call as a centrifuge running at about 70,000 rpm wherein the uranium 235 and 238 get separated and then you are able to take out the enriched uranium. But the centrifuge process is quite power intensive so there is a reason why many countries have not been able to go ahead with this already they are in need of power. Then this fuel has to be transported when I mentioned to you about the carbon dioxide emissions from the in case of nuclear power plants whenever we manufacture and transport a component it has to come on a diesel vehicle which is going to have carbon dioxide emission. So transport is very important stage in which the nuclear fuel will move between different parts of the cycle. So you have to be very careful that during the movement this radiation exposure should not affect the people who are involved it should not affect the public. So we have to see that they are packed properly shielded properly we use the word shield radiation shielding materials we use so that effect of the radiation is not felt outside. So these are the safety measures which need to be involved in the transportation. Just to give you an idea how a cask containing radioactive material looks like this is see a cask which is mounted on the train you see it's a good strain it is mounted and this contains waste or raw materials also this particular one contains waste nuclear waste which is also radioactive and this design is done in such a way that these casks even if they fall down they won't break. You will be surprised in the United Kingdom in the 90s there is a one person raised a question suppose this train carrying this radioactive material or radioactive waste meets with an accident what will happen. Believe it they took a train with one or two containers and containing the radioactive material and the train really was meant to have an accident and the cask fell down and nothing happened. So one thing is sure the methodologies which we are adopting for radioactive material are good and we have to need to the need is that safety at every level of this we should be safe so that radioactive releases or the radioactive contamination to the public and workers is minimal. Then the spent fuel let us take the spent fuel the fuel has been used now you have to take it out but it is at a high temperature it is not in a temperature you can handle immediately so it needs to be cooled it has to be put in a you know with proper cooling then only if you don't cool it that fuel itself can melt. So normally we have a spent fuel bay in which we put the fuel and you can see a simple system wherein from the reactor core the fuel is handled and then put to the spent fuel bay. One more thing is important that the geometry of the fuel bay and water should be such that it should not become critical we will see about this later. So this storage has to be kept for some time until the temperature comes down then in a dry cask you can transfer it to the reprocessing. And during that time and you transfer it even natural convection of air could be sufficient to cool the cask. Then as I mentioned reprocessing and the spent fuel is about 95% uranium-238 because all the uranium-238 doesn't get converted into plutonium only part of it gets converted. So also it contains about 1% of uranium-235 which is not fission. 1% plutonium and about 3% fission products. Besides you have neutron poisons like xenon etc which may be there and they are highly radioactive so in the reprocessing you separate the components basically we are looking for taking out uranium, plutonium and the waste containing the fission products. And based on the reprocessing output we can use the uranium and plutonium into fresh fuel and so that it is effectively we are reducing the waste. Now you might wonder that in the media there has been always thing that reprocessing should not be there. Reprocessing can lead to proliferation people can take the plutonium. Now USA has adopted this attitude that whatever is coming out of the reactor it is not used again it is just kept as a waste. But in this process the waste activity is high because of the presence of uranium and plutonium. If you can separate it and then use it in another reactor you are effectively utilizing the resources. In fact this type of approach without reprocessing is called generally as open cycle, open fuel cycle. Whereas what I was talking about the nuclear fuel cycle in which it is used back it is called a closed fuel cycle. And India per se has gone in for a closed fuel cycle because we want to effectively utilize all our natural resources of uranium. There is a process which is a well-known purex process which is used in reprocessing and just to get an idea what is the components of the purex process. You can have a look at this figure. It is a schematic figure in which it involves the disassembly of the fuel, the decladding, remove the cladding material of the fuel, then dissolve it using nitric acid. Then to extract the fission products they use TBP plus kerosene, it is tributyl phosphate and kerosene along with nitric acid. Then whatever is removed then goes further uranium and plutonium come in solution form, then you remove the plutonium and uranium separately. Whatever is the rest in the second stage after the TBP what is does not get dissolved is sent as high level waste and of course the rest of the process is as shown. Now the waste which is coming out from the reprocessing plant what we do, it is a very important part of the fuel cycle. We normally try to categorize them as high level, medium level or low level based on the amount of radiation. Now low level waste are practically produced at all stages like right from mining then your fuel fabrication everywhere they are all produced. Then intermediate level waste are produced during reactor operation or by reprocessing and the final high level waste is basically from the fission products which are taken out in the reprocessing plant. And that is which is called as a high level waste. Now this is high level waste is the one which we are saying that we can use back in the reactor so that we do not have any high level waste. To get a feel of this high level waste how much would be the content of high level waste? Very simple example I can give you. Suppose one person's requirement of electricity throughout his life was to be produced only through nuclear power then the high level waste will be equal to one fist that's all and that itself if you again put into the reactor there is no high level waste. So there is a fear that this high waste management is a very difficult and things it is not the quantity is very much less. Now how do we manage this waste? Low level waste contain radioactivity but this radioactivity is having a very short life so it is not very much it doesn't require a shielding and it can be just buried under the earth. But before burying up we just try to compact it so that and we also incinerate so that those material which are can be burnt they will all become action become it will be compact. So it will have only about one percent of the radioactivity of the whole waste one percent would be present in intermediate waste. Then coming to the intermediate level waste it will be higher surely it requires shielding you can't do without shielding then it makes up about seven percent of the volume and has about four percent of the radioactive waste is again in this. So this again has to be dealt with again stored for some time then the high level waste about which you have to be really worried it is highly radioactive as I mentioned it requires cooling and lot of amount of shielding also and it contains about 95 percent of the total radioactivity. So this waste is the one which we need to be concerned about. So what we do we have to immobilize the waste that is we have to see that the waste is not able to move so we have to make it immobile put it in some other material matrix in which it can it get bonded and it doesn't move. And that is where we find this borosilicate glass has been very good as a medium and borosilicate glass mixed with the fuel is able to hold the high level waste fuel very well bonded very well. So this is remains stable for a very very long time because they contain some of the long lived waste. This is just to give a figure of the process this process called vitrification that is mixing glass and the fuel high level waste and then trying to make this thing. So the glass is molten at about 1200 degree centigrade and we add the high level waste and then we pour it and then make it into a solid form and this solid form we put in radiation shielded casks and put it under the ground. Now coming to the waste disposal there are different types as one is near surface disposal and as I mentioned this is done for low level waste in all countries it has been done. Then deep geological disposal we are looking for basically for the high level waste because they are going to remain for a very long time. So we are looking at what you call geological areas where sites are such that they are not going to be approachable for a very long time. In the USA the Yucca mountain was the place chosen for putting these high level waste casks but they have been delaying due to so many reasons. In fact because of that the high level waste are lying in the plants and is not a good thing. In our own country we have looked at some geological repositories where the polar gold fields were there. Now practically it is all there is a lot of place available where so this is one of the areas which we think could be utilized. But till now even though our power program is not very big now it has not come to a level where there need to be a concern. In brief I can say that this part of the lecture we covered mining, we covered about the processing of the ore, then the enrichment of uranium-235 using the centrifuge and the diffusion process. We also had a look at the transportation aspect that we need to transport things properly in a radiation shielded casks so that it does not affect. So at the mining level also we need to be safe processing everywhere every step we need to be safe reprocessing. It is quite a bit of higher activity wherein we have to be very careful we deal with solutions also. Then finally the waste management wherein high level waste is involved and the waste disposal. So this lecture practically I have taken you through the different stages of how the fuel from its birth to its I shouldn't say death and its reuse. So this gives an idea about the thing so safety is involved at each and every step of this fuel cycle. Many of you might be interested to read through some of the literature. So I have just given the bibliography related to my these first two lectures and there are books many of them published by IAA on seawater desalination, hydrogen production. Then on nuclear safety by Gany Patrangeli and Lewis and the World Health Organization has produced some booklets on irradiated food. It is not that we say that okay irradiated food is not bad. It is all the result of research done over decades. So be sure irradiation not only preserves food, it avoids food wastage, it avoids you know bacterias in the food and you are able to have food at any time you want. May be it would be of interest to have a small assignment on this which I think you should take it up very simple. What are the different electricity generating technologies? What are the different applications of nuclear energy besides power I mentioned you so many other applications? And what is its use of radiation in medicine and industry and important? How do we treat the flue gas by radiation and make it safe? That is the sulphurated oxide, the nitrous oxide is how it is absorbed and then you do not get it put it into the environment, the sewage treatment etc. And last but not how you perceive risk? Thank you for a patient listening. Now in my next lecture I shall tell to try to give you some insight into the structure of the atom so that let us get back okay. We talked about fission but how does fission happen and how that concept of the fission. And hopefully with that background you would be in a better position to follow the further lectures. Have a nice day. Thank you.