Abstract
To situate the probabilistic safety assessment of standardized 900 MWe units made by the Institute for Nuclear Safety and Protection (IPSN), it is necessary to consider the importance and possible utilization of a study of this type. At the present time, the safety of nuclear installations essentially depends on the application of the defence in-depth approach. The design arrangements adopted are justified by the operating organization on the basis of deterministic studies of a limited number of conventional situations with corresponding safety margins. These conventional situations are grouped in categories by frequency, it being accepted that the greater the consequences the lesser the frequency must be. However in the framework of the analysis performed under the control of the French safety authority, the importance was rapidly recognized of setting an overall reference objective. By 1977, on the occasion of appraisal of the fundamental safety options of the standardized 1300 MWe units, the Central Service for the Safety of Nuclear Installations (SCSIN) set the following global probabilistic objective: 'Generally speaking, the design of installations including a pressurized water nuclear reactor must be such that the global probability of the nuclear unit being the origin of unacceptable consequences does not exceed 10{sup
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Citation Formats
None.
A probabilistic safety assessment of the standard French 900MWe pressurized water reactor. Main report.
IAEA: N. p.,
1990.
Web.
None.
A probabilistic safety assessment of the standard French 900MWe pressurized water reactor. Main report.
IAEA.
None.
1990.
"A probabilistic safety assessment of the standard French 900MWe pressurized water reactor. Main report."
IAEA.
@misc{etde_20740485,
title = {A probabilistic safety assessment of the standard French 900MWe pressurized water reactor. Main report}
author = {None}
abstractNote = {To situate the probabilistic safety assessment of standardized 900 MWe units made by the Institute for Nuclear Safety and Protection (IPSN), it is necessary to consider the importance and possible utilization of a study of this type. At the present time, the safety of nuclear installations essentially depends on the application of the defence in-depth approach. The design arrangements adopted are justified by the operating organization on the basis of deterministic studies of a limited number of conventional situations with corresponding safety margins. These conventional situations are grouped in categories by frequency, it being accepted that the greater the consequences the lesser the frequency must be. However in the framework of the analysis performed under the control of the French safety authority, the importance was rapidly recognized of setting an overall reference objective. By 1977, on the occasion of appraisal of the fundamental safety options of the standardized 1300 MWe units, the Central Service for the Safety of Nuclear Installations (SCSIN) set the following global probabilistic objective: 'Generally speaking, the design of installations including a pressurized water nuclear reactor must be such that the global probability of the nuclear unit being the origin of unacceptable consequences does not exceed 10{sup -6} per year...' Probabilistic analyses making reference to this global objective gradually began to supplement the deterministic approach, both for examining external hazards to be considered in the design basis and for examining the possible need for additional means of countering the failure of doubled systems in application of the deterministic single-failure criterion. A new step has been taken in France by carrying out two level 1 probabilistic safety assessments (calculation of the annual probability of core meltdown), one for the 900 MWe series by the IPSN and the other for the 1300 MWe series by Electricite de France. The objective of these studies was twofold: - firstly to check the safety level of the French units in the international context. - secondly, and considerably more importantly, to develop an additional resource for help in decision-making, allowing assessment of the relative impact of modifications to installations or procedures and to detect, once again in relative terms, any weak points. The importance of this second objective is of course greatly increased by the fact that the French nuclear facilities are standardized. When probabilistic safety studies are mentioned, emphasis is frequently placed on the first objective. Although it may be reassuring to find that the French power plants are well placed internationally, the absolute values indicated by the different probabilistic assessments are too dependent on the domain covered, the techniques implemented and the data used for it to be possible to make comparisons of safety levels on the basis of global results alone. On the other hand, the use of probabilistic safety assessments can provide interesting insights towards relative comparison approaches offering the greatest improvements in safety. In this respect, it is encouraging to find that the design of the 1300 MWe series represents an overall improvement over that of the 900 MWe series. The two studies which have been carried out must not be seen as an end, but as a way forward. Furthermore, it is possible to improve and add to them. This opens up two lines of action for the French safety organizations in the field of probabilistic safety assessments. Therefore, the latter plan to use the probabilistic safety assessments to help in the following fields: - grading safety problems and identifying any weak points; for instance, in carrying out the two assessments, two outage accident sequences were revealed whose relative importance had been underestimated. The international community has been kept well informed about them, - making periodic safety reassessments (earned out every ten years in France): this essentially consists of making a more quantitative assessment of the impact of any modifications made to bring equipment up to standard, - analyzing the accident situation operating procedures and the technical operating specifications, - studying the importance of the reliability of certain items of equipment or systems for safety, - analyzing the design of reactors of the N4 series and future types. As regards the evolution of the tool, the probabilistic safety assessments will be updated to allow for any modifications made to the units, the latest discoveries and the lessons derived from feedback of experience. Furthermore, the French probabilistic safety assessments may be supplemented to cover additional hazards, such as fire risks; extensions may be made to better appreciate, for various sequences leading to core meltdown, the corresponding probabilities of off-site releases, making allowance for certain modes of containment failure. This will involve overcoming a number of difficulties, essentially methodological, requiring a major analysis initiative which may well constitute a central feature of international cooperation. To conclude, it must be emphasized that although a major step has been taken with the completion of the level 1 probabilistic safety assessments of the 900 and 1300 MWe units, the making available of these tools has opened up a large additional field of study with much potential for improving the safety of these units. A major effort has been made to carry out these two studies. This effort will be maintained to ensure that they continue to bear fruit.}
place = {IAEA}
year = {1990}
month = {Apr}
}
title = {A probabilistic safety assessment of the standard French 900MWe pressurized water reactor. Main report}
author = {None}
abstractNote = {To situate the probabilistic safety assessment of standardized 900 MWe units made by the Institute for Nuclear Safety and Protection (IPSN), it is necessary to consider the importance and possible utilization of a study of this type. At the present time, the safety of nuclear installations essentially depends on the application of the defence in-depth approach. The design arrangements adopted are justified by the operating organization on the basis of deterministic studies of a limited number of conventional situations with corresponding safety margins. These conventional situations are grouped in categories by frequency, it being accepted that the greater the consequences the lesser the frequency must be. However in the framework of the analysis performed under the control of the French safety authority, the importance was rapidly recognized of setting an overall reference objective. By 1977, on the occasion of appraisal of the fundamental safety options of the standardized 1300 MWe units, the Central Service for the Safety of Nuclear Installations (SCSIN) set the following global probabilistic objective: 'Generally speaking, the design of installations including a pressurized water nuclear reactor must be such that the global probability of the nuclear unit being the origin of unacceptable consequences does not exceed 10{sup -6} per year...' Probabilistic analyses making reference to this global objective gradually began to supplement the deterministic approach, both for examining external hazards to be considered in the design basis and for examining the possible need for additional means of countering the failure of doubled systems in application of the deterministic single-failure criterion. A new step has been taken in France by carrying out two level 1 probabilistic safety assessments (calculation of the annual probability of core meltdown), one for the 900 MWe series by the IPSN and the other for the 1300 MWe series by Electricite de France. The objective of these studies was twofold: - firstly to check the safety level of the French units in the international context. - secondly, and considerably more importantly, to develop an additional resource for help in decision-making, allowing assessment of the relative impact of modifications to installations or procedures and to detect, once again in relative terms, any weak points. The importance of this second objective is of course greatly increased by the fact that the French nuclear facilities are standardized. When probabilistic safety studies are mentioned, emphasis is frequently placed on the first objective. Although it may be reassuring to find that the French power plants are well placed internationally, the absolute values indicated by the different probabilistic assessments are too dependent on the domain covered, the techniques implemented and the data used for it to be possible to make comparisons of safety levels on the basis of global results alone. On the other hand, the use of probabilistic safety assessments can provide interesting insights towards relative comparison approaches offering the greatest improvements in safety. In this respect, it is encouraging to find that the design of the 1300 MWe series represents an overall improvement over that of the 900 MWe series. The two studies which have been carried out must not be seen as an end, but as a way forward. Furthermore, it is possible to improve and add to them. This opens up two lines of action for the French safety organizations in the field of probabilistic safety assessments. Therefore, the latter plan to use the probabilistic safety assessments to help in the following fields: - grading safety problems and identifying any weak points; for instance, in carrying out the two assessments, two outage accident sequences were revealed whose relative importance had been underestimated. The international community has been kept well informed about them, - making periodic safety reassessments (earned out every ten years in France): this essentially consists of making a more quantitative assessment of the impact of any modifications made to bring equipment up to standard, - analyzing the accident situation operating procedures and the technical operating specifications, - studying the importance of the reliability of certain items of equipment or systems for safety, - analyzing the design of reactors of the N4 series and future types. As regards the evolution of the tool, the probabilistic safety assessments will be updated to allow for any modifications made to the units, the latest discoveries and the lessons derived from feedback of experience. Furthermore, the French probabilistic safety assessments may be supplemented to cover additional hazards, such as fire risks; extensions may be made to better appreciate, for various sequences leading to core meltdown, the corresponding probabilities of off-site releases, making allowance for certain modes of containment failure. This will involve overcoming a number of difficulties, essentially methodological, requiring a major analysis initiative which may well constitute a central feature of international cooperation. To conclude, it must be emphasized that although a major step has been taken with the completion of the level 1 probabilistic safety assessments of the 900 and 1300 MWe units, the making available of these tools has opened up a large additional field of study with much potential for improving the safety of these units. A major effort has been made to carry out these two studies. This effort will be maintained to ensure that they continue to bear fruit.}
place = {IAEA}
year = {1990}
month = {Apr}
}