 We will discuss now how to ensure that the staff are properly trained at the needed competency, but also learning from day-to-day activities and learning from experience, which are very powerful tools to improve safety during operation. The first element is to have the correct training of the staff. This is done through initial training and of course refresh training during the life of the plant. It is obvious that it is essential to get the competent staff, not only for the operating staff of the plant, but also the contractors, which intervene to maintain. The competency should cover not only the technical skills in various specificities, but also the specific risk of working in a new ground installation, such as the radiation protection and the industrial safety aspect. For this initial as well as refresh retaining, utilities and operators use a full-scale simulator for the operating staff and also use a mock-up on the work site for maintenance staff. It is important for the management to identify the training needs of its staff and also the training efficiency. It is a major responsibility of the management to look at this issue. You have here a picture of a simulator with on the right-hand side the control room, a replica of a control room, and on the left-hand side the instructor station on the simulator. And today most utilities have one simulator on each site. So now learning from day-to-day activities. It is important for the manager to bring staff to identify how to improve ways of working in day-to-day activities through the preparation of learning reports. And it's necessary to define some arrangement and a process to collect these learning reports, to analyze them, to decide potential improvements and to assign responsibility for implementation. It's very important to have a process that gives a feedback to the person who wrote the learning report of what action has been taken. These learning from day-to-day activity and this process of preparing learning reports, both for good action but also for near misses from error, is a very important tool to continuously improve safety of the plant. Okay, another important aspect and a way to progress in safety is to learn from incident and accident. We will see some major accidents, what happens, the lessons that have been learned from Srimal Island in 1979, Chernobyl in 1986 and more recently from Fukushima in 2011. You will have also a presentation of a detailed analysis of an incident that occurred in France in Blayet, a flooding problem that occurred in 1999. And we will describe at the end the operational experience feedback process. So Srimal Island, what happened? The events began with a loss of normal feed water and as was expected the primary pressure increase and also as expected a pressurized safety valve open. But it does not reclose, it did not reclose and so we enter a sort of a loss of current accident. But the instrumentation in the control room report the order to the valve, not its actual position. And so the valve being stuck open, the operator has the information that it was closed and he does not recognize the situation. So as expected for a loss of current accident, the safety injection was initiated automatically and began to fill the primary system. But the operator feared and overfilled of the vessel and he stopped the safety injection and during that time the loss of water continued through the open pressurized safety valve. So at this point in time the main primary current pumps began to vibrate and the operator stopped the pumps in order to not to destroy it. And with the pumps being stopped the water level settles below the top core level and there were no more cooling and the core could melt. And it took more than two hours for the operator to realize the exact situation and to reinstate safety injection. Safety injection was restarted. The accident resulted in the release of radioactivity in the containment building because most of the primary water was released in the containment building. But the containment played its function and only some minor releases were seen through the auxiliary building. Here you have a picture of the main characteristic. You have here the relief valve that's stuck open and so the water discharge from the pressurizer through this relief valve to this relief tank here and they have raptured disk on these tanks and given the amount of water and steam that get into this tank the raptured disk raptured and so the steam contaminated was released in the containment. Some water also fall in the sump and this sump was pumped in the auxiliary building and so some of the there was some radioactivity release through this auxiliary building and through the stack but very minor and there was no consequence for the public. This accident provided a lot of lesson to be learned for the worldwide nuclear community. The root cause that was identified covers design errors, procedural inadequacy, insufficient operator training and no feedback from previous experience actually in the two preceding years similar events begin to develop in other plants in the US or in Switzerland but in one case the initial condition was different and in other case the operator recognized sooner the situation something happens during this event but should the operator at St. Mary Island had learned about this experience probably he would have acted differently and there would be not no consequence. So from this accident the very significant safety improvements were made especially on the man-machine interface. Through the control room economy to provide better information in a more synthetic way to the operator the new types of EOPs that I mentioned the state oriented were developed because there was no sufficient emergency procedures to cover the situation where the operator at St. Mary Island had to face. Safety panels were grouping all the main safety parameters when installing the control room for the operator to better recognize the situation. Of course the type of safety valve that failed at St. Mary Island was replaced with new types and that was the first time that a Cormelt scenario Cormelt was supposed not to happen before this accident and the reality shows that the Cormelt situation could occur and so most of all the following consideration in the safety analysis includes some Cormelt scenarios to be taken into account and as mentioned at the beginning of this picture what St. Mary Island showed that it's very important to look at a small event that could occur because the small events could be precursors of much more severe and it's important to detect these small events in order to prevent them and avoid that they turn into more severe sequences. Now the Chernobyl accident it's a rather complex one and the root codes were soon identified first there were some gross design errors the core of this type of reactor is the RBMK the core of this reactor is not stable in all conditions it's stable at full power but not that partial power another design error was the fact that when inserting the control ward it begins to increase reactivity instead of decreasing it and last but not least, this type of reactor has no real containment function that was the case in most western plants so besides the gross design errors there was also human and organizational deficiency the operating staff was under pressure from some engineers in Moscow to run a specific test and the test was actually begin in unauthorized condition especially the fact that instead of starting the test from full power the reactor was stable it was begin from a partial power and the core was unstable and as they were under pressure to make this test and that was during a night shift they decided to turn off all the safety system and it was clear from these organizational and human aspects that safety was not the top priority the top priority for the crew was to make this test that was required by the engineers so this accident has a terrible consequence because there was a power excursion, the graphite got fired a huge plume spread all over Europe 20% of all the efficient product contents of the core were released and 135,000 people were evacuated unfortunately they were not evacuated just after the accident but several days after and several people were contaminated so the lesson learned from Chernobyl of course in Russia many designs were made the design change was made on these RBMK reactors which are not applicable to western type reactors because this is very typical of the Russian design but this accident shows some more lines on the reactivity incident and accidents and so on the western reactor some studies were revisited on this kind of transient and accident and modifications were made to better control them but the most important worldwide lesson from this accident is consideration of social organizational factors in nuclear safety and the introduction of safety culture concept and we will come back a little bit later on these aspects Fukushima so a severe earthquake strikes northeast of Japan and all the reactors behave as designed so they were just automatically shut down and nothing happens serious during the 21st minutes some the cooling system remain in operation powered by batteries but soon stop running because the grids because of the earthquake has been destroyed and about half an hour after the earthquake the tsunami floats the four units and knocked down not only the external but also the diesel generator the internal powers so there was no longer any means of cooling the reactors and the core begin to melt some hydrogen was produced the containment was over pressured and they had tried to vent the containment in order to release some of the hydrogen but it was not successful because there was no power to open the valves and the pressure inside was too high so this explosion occurred and with the consequence that we have seen the three of the reactors had some core melt so what was the root causes of Fukushima first there was insufficient protection against the tsunami that was something known but nobody act to correct this situation and for instance to increase the level of the dike another organizational factor was the fact that the regulator was not independent from the government and so it was not in the position to require the operator TEPCO Tokyo Electric Power Company to make the modification needed to protect correctly the plant against tsunami another element was inadequate emergency organization there was a lot of difficulty of course because of the tsunami but also because of the internal organization of all the TEPCO company with no sufficient training and last but not least a deficient operating experience feedback process because some of the weak points of this kind of plants was identified years before by Generic Electric the designer of this kind of BWR and modifications have been made on most similar units in the world that was not taken into consideration at Fukushima so what are the lessons learned from this accident the first is to consider more severe external hazards in the design most of the plant have a design basis for the external hazards and we have seen some of them in previous parts but extreme more severe hazards could occur and should be considered so more margin should be introduced in the design for taking care of this kind of situation it is also necessary to consider a resilience provision to cope with the plant blackouts a complete loss of power and also a complete loss of cooling this is the various situation and that was the actual condition of the plant at Fukushima another aspect is that usually most safety analysis concerns one reactor even if there are several reactors or several plants on the site in this particular case there were four units on the site and that complicates the situation and in terms of staff availability it is important to consider that the site could be affected and several plants another lesson is to reinforce the independence of regulators and since then in Japan there has been a large organization of modifications of the regulator which is now completely independent from the ministry of industry and after this event the European Commission required some tests on all plants in Europe that were called stress tests and the idea was to assume on all European nuclear plants a condition similar to Fukushima to check how these plants will behave in this kind of situation and this review was reviewed by a peer process between the various regulators in Europe so a lot of modification has been made after Fukushima so from these accidents it's clear that every utility, every licensee should have an operating experience feedback process that is arrangement to collect incidents to analyze them and to draw lessons and to implement them and this is the first responsibility of the operator but the regulators have also developed a set of criteria defining those safety-significant events and incidents that should be reported and made public and disseminate between the worldwide community but not only significant events should be reported but also the less significant ones because they could underline some potential negative trends and so it helps to take action before anything serious could happen this process of experience feedback should be developed not only on a national level but also at the international level and regulators and utilities operators have developed incident reporting system to share the experience worldwide both between the operators and regulators and these incidents and the lessoners are stored in data banks that are available to everybody and this database, data bank could be used to update probabilistic safety analysis as we have shown previously