 மங்கடி நடந்தும் நன்றி எந்தங்களை அவரையும் நான் மீ்முடிந்து உரு அற்பற்றமிலிருக்கிறோம். சந்திக கரண sónக்காடி விருசை watersミー-ி விளிகக்கை பட விருஹர்பல் வாடல் நான் ஒரு முன் புல் முள்ளிடைய எக்கின்ம். எந்த வாசனை சாபகாகக்கருப்பู้ல் உனக்கு இன்னை பேர் விதாரி. அதனால் இன்று développுக்கில் சண்டு பாராத்துவிட்டார்கள். ஏன் நப balconையில் இருகிறார்? என்னுடைய சிறந்தமகள்? வேறு首先 ஊதிகிர்ஸ் சாபக்கலை, நலக்கினுத்து, நப்பிச் செல்ல should have people who have the capability to do the jobs, operation and other requirements. They must meet some minimum educational standards. இது என்னுடைய நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ்ச்சியில் நிகழ் நான் அனைத்துக்கொண்டு, நான் அனைத்துக்கொண்டு அனைத்துக்கொண்டு இருக்கிறோம். அதிக சார் bend பார்ப்பு கொழங்டியதால்ality அற்படமுறை வர்க்கு inicial வரவில்லைல்வு ஆகந்தால்குக் கடவுரி நினைத்து , நீங்கள் வருங்களைக்கொன்ன செய்கிறாதற்கத் அன்னுக்கும் ஏக்கிறார்கள் கேள் நிறுவன் அற்படம் அறுவு எதுவர் அடுத்தில் பச்சியுள்ளுக்겠க Banкое நதுகலந்த அவர் உன்னுடைய தொடர்பு ஆயம்மை குறைச்சியிராக அனுபறித்தோடு விவர் உண்களை அதன்ாதச் செயல்வார்கள் அவன dormitory remembrance ஓல்ரெ டிலிமை விருந்தது நிச்சந்தத்திக் கொடும்கு முன்பு அழைத்து இது உய lock ஆழித்தனதை அழுங்களுக்குία் அருந்தłąர்பு. சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்து, சிறுத்த சொன்னர்களை வாப்ப நேர்களையில் இண்ணா Mickey ஙார்படிions செய்கி Erfahrung நிறுகலும் செய்துவிட்டது செல்லும் தரணி செல்லும்லை உண்டிய intersectந்தநொ serait்டீர்கள் students இன்மும் கூட்டு நான், improvesப் பளைக்கு சந்திக்க வந்து புணம் சізக்கிக்கொள்ளன் நே aussi, நினைருப்பம் நேசியாயிற்கு சுக்கதி, திற்கம் இன்சரிம் நிலையுடைய பளைக்கு செய்த்து ஆ ŵா நீகு ஓர்பிங்களாக நூல நிருப்புர நிகழ்ச்சிக்க mango குறவுsized, lien சொ aquíக்கு நீதாட அனைத்து ஓட்டினொண்டு நிச்சயமாக ஆது ஏன் எநரிய சரிது செல்லும் இல்லை. நான் தயார்க்க perpetual ஓட்டினொண்ட நிச்சயமானவிற்கு அப்படியான கமைத்தினை எல்லாம் ராணیاனினரமை துணைப்பு முடி பாக்கும거든요. முகத்தில் முகம்வும் தற்றி பெறழ்ந்தில் மகிழ்சி அல்லது இருதிக்கை பில't மரியுழ். இந்தான் சில்ல mid then இந்தம் இடாwer Anish அல்லது அனைத்தற kaik்காடு வரவேன். ஒலுங்கு நில முகது and மீயுற்கானு கணைக்குoid ஆதலத்தில் சித்தாய். சஷ்ண் பதிவகு Kobe சென்னறத்தில் கதுக்தில் Ll அங்கு நினைவு பித்தில் சிர்ந்தாக இருப்பம் உன நல் எஹந்தப் பidsல் வழக்கலாகத் தைகி அறைக்க நேசியாகச் செல்லக்குக்கு ஏத்த ank ச நேசி சுறைய மன்னுத்துகிற்ளாக நிசை குளைய குறுவார்B அனைத் தொன்றிய பசத்த வருத்ததில்하면서 சிறிப்டு வ வழக்கothermal 수가 பேசியரிலுக்கு நம்முன்ன போல்ưegt முடி துறண்டுு ஒவசாரிலுக்கு வகுவிக்கத் தொடர்புகள் நீக்கு manipulating விஅக் komenத்தில் சென்று வருத்தாலுங்கள். ஆனால் தோல் இன்னுக்கு மரியம் காதகாது பறகு நகும் பயன anx ரிதில் ரூ mai, இங்கிருடைய polynomial் என்னைப் போட்டுக்கொண்டும், Revolution Of The紹, அப்படியாக இருக்கிறதா? ஆனால அவ்வளவு கேள்கில் சந்திராப்புகளும் நிகழ்ச்சிச் செய்த மீச்சி, காட்சிமாகச் சீர்க்குச் சார்க்கப்படி, உரைந்து கீழ்ச்சியுறை சமர்யுப்பதை என்கு இணுகம் தேவைத்துவிட்டும், சர்க்குப் புரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீர்களுக்குப் பிரிந்துகொண்டுகிறீ ஆகியும் இருக்கைத் தெரியும் இ dictate your position, history has to send periodic reports to the ions of ARB. சுர்க்கப் பையிப்படால் என்ப murm Veganopingுடன் வீட்டில் செய்தார்யாது புரிந்தைய், விஷ்சை அத்தி நாடிக்கிக்கொண்டிருக்கிறேன். கூர்க்கை பிடிப்படுத்து,матதையாத்தியாத் இதைப்படாது சிறந்திப்படியற floating குற்ற பார்க்கும். டெசியாகப்பட்ட விஷ்சையுசையுச் செய்து, நிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலிலில அலுமையோசி அனைத்துக்கும் இ துணைச் சந்தாயா? நீதான் சம்னித்து இற்கு அலுவந்து உணவியில், சர்க்கம் செய்துக்கொண்டு, நேரத்துக்கொண்டைத் தேர்வவர நரிதாயா? அப்படியே ஒதினம் டெடிந்தா abortions சொல்லுங்கள Asíரோக முறைத்த புதில் அனைதால் செய்துக்கொண்டேன். ஓ ஏன் machinery Ikusczyć சிமிகஙкடம் வாழ்க்குகளுக்கு continues சாத்திக்கவல்லையில்ணைச் சதிந்துவிடுகிறinctக் கண்டிறிப் கடுதும் சுணம்கு ஒரு நிறந்து எதில்像 அEROுறைகளை அவனையில் அவனையில் புறக்கு வைத்திருட்டம் முறை ஒழுது 새ன் புறந்தேன். இனைத்தை மற்று செய் surreal திடம் வருகிறோமல், நிகமோத்தில் எதற்கா ஏழுகாறல்ு முதрезும் பொருப்பாக இருக்கும். இனி வணக்கம் வெளியில் என்று நலக பயன் காலை வந்திருந்து concerts' த எந்த முதல் க நின்றிவ நிறு போதும். கிறகால- நின்றிவ நிகுதியனி வருத்தன் say every 15 days or every one month, all these are written down. And when you inspect them, you fill in when you are inspected and what is the health reports. So all these reports, when the AERB team comes, Regulatory Inspector team comes, it will go through and see whether you have followed. அந்த சரி, அந்த ஆற்றைகளுடைய சடிட்டது, neighborhoodrum would go further deep into that, then suggest the corrective measures. Yotsalo Let us say that the first authorization for a regular operation was given, and now periodic safety review has been conduct. திரு முதல்சீட்டுród், ரேவையுடன் சிறப்பி ரேவியுdish சிலு��ளிக்குத் திரு நிருந்து, சின yılேயியுறிலுங்கள்ம நிலு அவகா ரவையின் அறுகைலிம் ஒரி ரேவியுஞ்சத்தில் சிறப்பி சிலுங்கள் உரிலுங்க சோடர காபிその விளைவின்ன próprio ஆவண்டுரி திடங்கிவிட்டிருந்து நமீண்டு demokratiy சிரம்பிнако கூற personnage பளக்கப் சரம்திை. எனக்கு நாங்கள் விண்ணும் ஒன்று புண்ணம் விண்டும் பழக்க்கலும் நகன்மகாளர மாதகைக் கூட விண்டும்தான் உள்ள சட்டிக்கலாப் எல்லாகத் தீண்டு,திந்ததுக்கொண்டு போத்து, சரிய நாடதார்ச் செய்யுங்களுடன் பார்ணம் குறைம் இில்லாதுயMother- shadd experi ஆசைக்கை непிறவு நகு,எதற்கு,வாதங்களிடம் கருட்டு, ஓர்கும் டிங்காக நேற்றுகிற 냄새 lettuce அனைத்துந்கச் செல்லுங்க நாட்கள் எக்ஷ்மிர வநமை செல்லுங்கள் நெல்ல பீட்டாப்படறுகு அனைக்கு மூன்று. அப்படியட குப்புகப்பட செல்லுங்கள், அந்த வகுறைக்கு மணிந் பிரியார்த்திருக்க முடன்தான் ஓர்காறடினம் ஏடியverted பதினால் அனைஜு Tôi் சென். குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம் குத்தம கருப்பிரிந்து கருப்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்பிரிந்து காட்ப சிம்புள் but very important that during this period of 30 years some of the design rules may have changed of course may be the earlier rules were very conservative based on which we estimated the life to be less only 25 to 30 years but today more knowledge is available about the material performance material characteristics material response to temperatures and pressures our knowledge base is more so this when this review is done with the latest data we may be able to extend the life plus should there be a safety improvement which could not be implemented in a regular way it can be implemented. So here this sort of reviews are very useful how is the review conducted as we have seen it is a multi tire review all the plant operations are actually reviewed by a station operation review committee we normally use the word SORC acronym SORC we never use the full word is a SORC. So every station has got a SORC at Kalpakam you have got an SORC for the heavy load reactors because they come under maps we have got a SORC for a fast media test reactor plant everywhere there is a station operation review committee then in the case from here at the utility headquarters that is the NPCL headquarters we have the safety review committee the SORC will give the operation inputs and the nuclear power corporation will draw the designers and the quality assurance exports also and review the whole operation and findings having done this it goes to AERB. So above this line is AERB in AERB every unit has got a safety committee which is looking after the review of that plant so that the people are familiar with what has been happening in the plant they are familiar with the history of the plant. So it is easy to make a good judgment for them to give the clearances. So the unit safety committee does this job having done this the unit safety committee gives the recommendations to SARCOP which is the safety review committee for operating plants and SARCOP mind you it will go through the things should it have some clarifications or it feels there is need to look into the matter in more depth it appoints export committees. Many times the export committees consist of people from outside the department of atomic energy and from different units so that you have the expertise or the wisdom of all getting into resolution of the plants. Now SARCOP also does a quarterly progress report of all the plants and sends it to the atomic energy regulatory board which meets every quarter and discusses these reports so that it is satisfied that the all the plants are operating safely. So the AERB that way in its newsletter it gives what is happening to the different plants what has happened and it is quite open and transparent and available to all the public in that website. Website is www.aerb.gov.in. The regulatory inspection during operation what he talked earlier was the renewal authorization that is periodic safety review and application for renewal of the little review for renewal but here it is during operation. So here during the operation twice a year normally the units are visited the plants are visited we do have industrial safety experts also there besides the experts on the nuclear area and all of them go through all the documents all the thing they also question. They practically do the audit the utility does everything but they do the audit whether the utility is doing as per the procedure. So sometimes when during these inspections if the regulatory team finds that things are not going fine it can recommend to AERB to stop the operation of the plants. So basically this regulatory inspection is to see compliance of all the regulatory requirements by the plant or the utility through review of records and other documents maintained by the utility. So that is what is the during operation. If you say what are the list of items in brief audit of operation maintenance and quality assurance programs when I say maintenance as I told what is the frequency of maintenance should there what is the preventive maintenance schedule what is the schedule of surveillance all those things will be there. So whether it has been done as per that. Then whether the plant is being operated as per the technical specifications whether they have not crossed the limits if they have crossed the limits have they reported to the AERB and taken clearance or not. Then whether the license staff is available in all shifts in the different areas of the plant in control room the local centres whether they are available again this is through a documentary check. Then what about the health physics people are they taking data on the activity and radiation doses received by the people are they maintaining the records of the pocket dosimeters or the TLD badges whether all the records are being done. Whether these badges are being sent for counting all sorts of these whether how they are being followed is seen through audited by through the documents. Then what about the emergency preparedness exercise whether any drills have been conducted by the plant. Normally once in a year we are supposed to have a drill to see that all the what you call establishments in and around the plant are ready to carry out the actions needed during an emergency. So it is something like you know training the people so whether it is being done as per the regulatory procedure. So that is one step then licensing of the operating personnel as I mentioned it is a very mandatory requirement that personnel in different facilities should be licensed and qualified. We have a manual for this called as the licensing procedure for operating personnel and also a QA manual for station licensing examination. Here the purpose is to check the their competence their depth of knowledge and any skills for operation positions. How fast he is able to think no doubt all these are tested through a set of examinations, written examinations followed by interviews. One thing which I have forgotten to mention earlier today it is mandatory that all nuclear power plants have a power plant simulator. What is a power plant simulator? The power plant simulator is basically it is a replica of a control room but there is no plant. The plant is modeled and it is in the software but all the switches are there so when you say pump start on the console it will initiate the pump start and the flow will increase. All these things can be seen on the control room panels. This as I said it is a replica control room the operator is exposed to the same environment as he would be exposed to in case of an actual reactor. There is also a training console which is kept by the training supervisor and what is the role of the training supervisor? Let us say the plant it should be started up so the procedures are given so the engineer shift engineer starts the plant and whatever he does step by step is recorded and at any stage if the person is deviating from the procedure the training supervisor will caution him. But here it there is no real plant it is only a simulation so the operator gets a feedback through that similarly the training supervisor gets it also on his console. So this way the operator is a supervisor is able to guide then next step operator responds to different events. Let us say there is a power failure there are a certain set of actions that he needs to take place should be undertaken by him. So what the supervisor will do he will have a software key by which he can simulate a power failure situation. So then the response of the shift engineer or the operator will be observed and then recorded and then they will be assessed so this way the training is made fool proof to the operator. Now earlier reactors that was not compulsory but of late last 10-15 years it is compulsory and we have operation training simulators. When you go to the simulator room you will feel as if you are in the control room of an actual plant. So these after these examinations and interviews the licenses are given for a period of 3 years to the operating personnel and then they are renewed thereafter. Surely along with this there is a cash incentive for them by giving some special allowances. Now we talked about reviewing the safety after some 20 to 30 years of the plant life. We want to reassess whether the license can be given but let us say during the operation of the plant sometimes there are changes needed due to some operating experience. Or some incident happening somewhere else. The best example is of 3 mile island pressurized water reactor. The moment the accident happened in the 3 mile island there was a review and as we saw earlier lot of changes in procedures was sought. Operator training was needed to be enhanced all such things are there and there was need for better instrumentation of the plants. So how does one go about so that means you have to do some safety upgradations so how do we do that. So we have stipulated for all the old operating plants whenever any change happens or any incident happens we have a thorough review carried out by the utility submitted to AERB and we see whether there is any safety concern. If there is a safety concern we will do that improvement but if it is not a safety concern then we prescribe some procedures and continue to operate. Now this applies to basically 3 plants. The first 2 units at Rajasthan power station units 1 and 2, Tharapur 1 and 2 they are of the boiling water reactor and MAPS 1 and 2. Subsequent to that more or less in the candle reactors there has not been much change. Now let us come to Rajasthan unit 2. We did a review for this reactor which was commissioned in 1981 and what upgrades and modifications needed they were finalized by the utility. And one of the important things compared to the, it was earlier they were using zircolyte 2 for pressure tubes but based on the experience of swelling, bulging etc. of these tubes we had developed a zirconium niobium alloy which was tested for a long time. Tested means under the irradiation atmosphere in reactor, actual reactor and this new alloy was found to be suitable. In fact for that matter in the heavy water reactors which use thermal neutrons the flux levels are low but in the fast reactor like FBTR the flux levels are a decade higher. So when we wanted to irradiate this and get its full lifetime irradiation data, we irradiated the zirconium in FBTR test reactor so that in a shorter time we could get the information of the effect of radiation and temperatures and we could come out with the zirconium alloy. And these were needed to be replaced the zircolyte 2 pressure tubes. So in 1996 normally every 10 to 15 years there is a need, earlier there was a need to change these pressure tubes. So at that time we put the zirconium niobium alloy. One more thing we did at that time was to have the supplementary control room. Now you have a main control room where you have carried out all the important operations. But a need was felt that should there be a fire in the control room many operations practically you may not be able to do any operation. So most important operations which are required for safety were also wired to another control room called as the supplementary control room. Of course today all the reactors need to have the main control room and a supplementary control room or sometimes it is also called as an emergency control room where most of the safety operations can be done from that. And that is provided in another building so that there is not chance of a common cause effect. Also in the Rajasthan 2 we put additional diesel generators so that it could meet all the requirements. Then we come to the boiling water reactors in Tharapur. As you know the construction started in 64 and it was commissioned in 69. Then from time to time we had some operation problems. So we felt that there is need to improve some of the components and do some safety upgradation in some areas. Here you know the general electric company which has built a large number of boiling water reactors. From time to time they keep on giving out the experiences of the different plants. So we not only have the experience of Tharapur we also have the experience of other boiling water reactors. So based on these we found out that we need to do the following. We needed a lot of modification in the emergency power supply system to the plant. As in the case of Rajasthan unit 2 we needed to add more diesel generators of higher capacity and not only that segregate these diesel generators to avoid a common cause failure. I mean common cause means to be a common cause like flood or could be fire. Then other systems like the shutdown cooling system whether any of the shutdown cooling systems are shared with any other things. If wherever sharing was there we wanted to remove the sharing plus the spend fuel cooling system that also we needed some improvements. Then on the emergency feed water supply we felt the need to add independent set of pumps. Again addition of a supplementary control room and improvement of the fire protection system. Here I would tell one thing it does not mean that it is unsafe it is better operation leading to less of troubles. But in our reactor terminology more or less we consider both alike everything is towards safety. Finally a plant should be available plant should be operate safely without even minor issues that is our aim. So this was all done. Then another requirement from the regulatory authority is about the probabilistic safety assessment. During my lecture on the analysis of different events I mentioned to you about the deterministic approach and the probabilistic approach. So deterministic approach is one thing but for incidents which are a very very low frequency whether the margins we can have high or whether I should postulate an event whether it is really happening. So these sort of assessment based on the what you call probabilistic calculations is now mandatory. So we have carried out the probabilistic safety assessment basically level one what we call for all the internal events and we estimate what is the probability of a core damage. And it was about 7 x 10 to the power of minus 5 per reactor year. Then not only that seismic re-evaluation that means we carry out the seismic analysis of all the systems once again. And because we now have the latest data on the ground motion parameters we have the structure actual when earthquakes have happened we have got the data. So we found that in certain areas basically the auxiliary systems if we strengthen the supports things would be nice. See the auxiliary systems per se are not going to endanger safety but they are going to affect the availability of the plant. So we have gone in and strengthened those structures. Of course after the TMI 2, 3 mile island 2 accident in the United States in 1979 again we look into the whole designs even though we didn't have a similar reactor at that time. Now Kudangulam is similar to that. So we found that again a lot enhancement of the emergency feed water system was needed. So that we implemented. Then we also augmented the capacity or you can say the inventory of the equivalent system so that it could give flow for more. Basically in the case of the Tharapur atomic power station then in some cases we wanted to have remote operation of some of the valves so that without getting any activity the operator could operate. So this is a safe operation. So there we did some modifications. Then in the case of PHWRs we also included a high pressure emergency core cooling in addition to the existing systems. So that we have a more defense in depth philosophy of providing cooling under all cases. Not only that, emergency operating procedures like 3MI 2 surely we didn't expect it happen. So what should be the emergency operating procedures under the new set of events. The next of course accident after Chernobyl. So after 3 mile end was Chernobyl in Russia. So again AERB undertook a detailed review and this is very important. One thing was the design of that reactor or a similar reactor of design reactor is not existing in India. Neither Tharapur, none. So the design itself had some fault of the Chernobyl reactor. Again it didn't have the containment as I mentioned earlier. So the major aspect of learning in this was emergency preparedness aspects. Then nevertheless we also started examining our reactor behavior under low power operation where in the case of Chernobyl there is a positive reactivity coefficient. We again analyzed our reactors and reviewed whether under any condition it is possible to get into a positive reactivity regime. So having done that only thing we needed was to have a look again at our emergency plants both for on-site and off-site emergencies. When I say on-site emergency it means the emergency which is limited to the plant and not involving the public. Off-site means which also includes the public. So all these were in the nature of reinforcing the existing practices with checks and balances. Then we had our own event of fire in the Narora Atomic Power Station. Though I have talked to you about it in my earlier lectures, nevertheless it is worth repeating for sake of continuity. This incident happened in the Narora Turbine. The last few stages of the turbine, the blades started, you know, the clearances between the blades and the casing came down as a result of vibrations. And the vibrations of the shaft were due to imbalances, severe imbalances in the thing. May be the blades had moved away and these blades touched the casing. When there was casing was touched, there were sparks, you know, 3000 rpm blade touching a static component. There were sparks and not only that because of this imbalance, the generator hydrogen seal was damaged and hydrogen came out. Hydrogen is normally used to cool the generator because the cables have got the I squared R loss, heating loss as current passes. We had to keep them cool so that the insulation life is long and lengthened. So we use hydrogen and this hydrogen came out and this spark ignited the fire, ignited the hydrogen. The fire, what happened? The fire spread to the cable trays, from the cable trays, the relay panels and it also went very close to the control room. Then, what the operator did? He tripped the reactor by manual actuation and initiated cooling down of the reactor. In the meantime, the control room equipment also fire came into the control room and damaged the power supply and control cables. When this happens, what? You have the electrical power but you are not able to control your pump. You are not able to start the emergency coolant pumps which is required to cool even in a shutdown state. That is what we call as the decay heat removal. So this was needed. So effectively you can say diesel generators are available but we could not start the pumps. So in effect, it was a loss of offside power, equivalent to a loss of offside power and a loss of onside power. So what we call as station blackout and this lasted for nearly 17 hours and also the operators could not work in the control room due to heavy smoke thanks to the training. If you recall the engineered safety features, we have got different levels of cooling and last but not the least, we have fire water safety pumps. There is fire water pumps which are operated by diesel generators directly, not the station diesel generators. So operators started those and maintained cooling of the plant. Of course the fire per se was put in about one hour to one and a half hours but the cables were damaged so the operators resorted to the fire water to quench the heat in the reactor. There was no failure of fuel, there was no radiological impact of this incident and nothing happened to the public. But then this is an event which is not very good, something like a common mode or common cause failure has happened. So this was very much in detail looked at by the atomic energy regulatory board. We found that everywhere independence was there of the signals, the shutdown systems, everything. But then when these cables were entering into the reactor building, they were through a common penetration. So the common penetration was the cause of the fire happening. So they re-rooted all the power and control cables and true independence was maintained. And also not only that, providing additional firewalls so that the fire should not spread like fire barriers at the penetrations wherever and whether fire retardant cables wherever possible, these were introduced. Thereby, the chance of a fire affecting all the systems was minimized. Then of course having done this continued surveillance was improved. Then the fire detection systems, they were also some improvements were done. Then the ventilation system of the control room, we found that control room could not be habited due to the smoke. So what about the ventilation system for the control room? Then last but not the least, the design modification to the last stage turbine blades. Here you see these operate on saturated vapor. It is not superheated steam. So when the saturated vapor you use, the last few stages do have moisture and moisture is the one which can cause erosion of the blades, thereby causing these vibrations and imbalances. So this is also an area where material improvement and other things were necessary and we have strengthened these blade designs. Last again, all the emergency operating procedures in case of a station blackout, we have again improved. Now we will continue of further regulation of AERB in the next lecture. Thank you.