[en] un-isolable primary coolant leak incidents, which occurred in Dampierre 2 and Dampierre 1 in France in 1992 and 1996 respectively, Farley 2 in the United States in 1987, Tihange 1 in Belgium in 1988, have revealed the existence of fatigue cracking phenomena on terminal portions of safety injection lines connected to the primary circuit. The incidents in Germany in 1986 and 1995 respectively and the Oconee 2 incident in the United States in 1997, have shown that this risk also exists in un-isolable lines of the chemical and volume control system. The Genkai 1 incident in Japan in 1988 has pointed out the possible occurrence of such fatigue phenomena in un-isolable sections of the residual heat removal system. Finally, the Loviisa 2 incident in Finland in 1997 has confirmed the generic nature of the phenomena. An IPSN-GRS working group was established with the following objectives: on one hand, to review these incidents and assess the measures taken by the operators and designers in order to better understand these phenomena and prevent them; on the other hand, to propose recommendations, taking into account the measures already implemented, in order to prevent this type of incident from recurring. From its analysis, the IPSN-GRS working group concludes recommendations to be considered by operators and designers to reduce the risk associated with these phenomena, both in operating plants and in future plants. These recommendations are concerning: - the piping links between the primary coolant system (RCS) and its various auxiliary systems and between the various RCS auxiliary systems; - the tightness of isolating devices separating a hot fluid and a cold section, a cold fluid and a hot section, a cold fluid and a hot fluid, and a cold section and a hot section; - the condition of supports controlling the position and movements of pipes and components; - the soundness of piping sections that could be the location of thermal phenomena (thermal stratification, mixture of hot and cold fluids, thermal sleeve, etc.); - the tightness of the reactor coolant system; - the tightness of auxiliary systems connected to the reactor coolant system; - the exclusion of any defect and surface or material conditions that could initiate cracking and encourage propagation; - the exclusion of any untimely and unwanted contact between pipes and surrounding structures that could induce additional stresses. (authors)

[en] Highlights: • The important role of Operating Experience Feedback is emphasised. • Events relating to cracks and leaks in the reactor coolant pressure boundary are analysed. • A methodology for event investigation is described. • Some illustrative results of the analysis of events for specific components are presented. - Abstract: The presence of cracks and leaks in the reactor coolant pressure boundary may jeopardise the safe operation of nuclear power plants. Analysis of cracks and leaks related events is an important task for the prevention of their recurrence, which should be performed in the context of activities on Operating Experience Feedback. In response to this concern, the EU Clearinghouse operated by the JRC-IET supports and develops technical and scientific work to disseminate the lessons learned from past operating experience. In particular, concerning cracks and leaks, the studies carried out in collaboration with IRSN and GRS have allowed to identify the most sensitive areas to degradation in the plant primary system and to elaborate recommendations for upgrading the maintenance, ageing management and inspection programmes. An overview of the methodology used in the analysis of cracks and leaks related events is presented in this paper, together with the relevant results obtained in the study

[en] In a collection which aims at providing those who are performing activities in relationship with ionizing radiations, notably in the nuclear industry, with elements of cultural technique related to the prevention and to the management of associated risks, this volume addresses pressurised water reactors (PWRs) and more particularly those which build up the French nuclear fleet. A first part presents general contextual elements: health and biological effects of ionizing radiations and the system of radiation protection, organization of the control and regulation of nuclear installations and activities in France, the international and societal dimensions, nuclear reactors as complex social-technical systems and the importance of organizational and human factors. The second part addresses safety at the design level: development of nuclear energy based on the use of uranium-235 and some notions of PWR physics, general objectives, principles and fundamental concepts of the safety approach, safety options and considerations at the design level, study of operating conditions in the safety deterministic analysis, the accident with loss of primary cooling, the particular case of steam generator tubes, the taking of aggressions of internal or external origin into account, complementary event domain, development and use of safety probabilistic studies, specific aspects related to fuel warehousing pools, integration of organizational and human factors during the design of installations, study and taking into account of core fusion accidents, new generation reactors. The third part addresses safety during exploitation: start tests of PWRs, general rules of exploitation, rules and practices with the return on experience of events, return on experience due to a weakness of the initial design of reactors or to the maintenance quality, return on experience related to interventions, to electricity sources and distributions, or to internal or external aggressions, strengthening of the protection of sites along an estuary or river (examples in Le Blayais and Cruas-Meysse), the taking of organisational and human factors for the exploitation of installations, the maintenance of installations, in-service monitoring and control of equipment, managements, control and evolutions of the nuclear fuel, the compliance of installations, periodic re-examinations, optimization of radiation protection and limitation of doses received by workers. The fourth part addresses the accidents of Three Mile Island, Chernobyl and Fukushima, lessons learned, and the management of emergency situations. The fifth part is dedicated to studies, researches and developments in the safety of PWRs, and to simulation software

[en] Everything that is important to know about pressurized water reactor safety in nuclear power plants is compiled in this work of reference, from safety fundamentals and reactor design to provisions for managing a radiological or nuclear emergency. The book narrates the determined and continuous quest to enhance nuclear safety. Jean Couturier, coordinator and senior editor, covers the forty-year history of evolution in the safety objectives, approaches, analysis methods and assessment criteria that have defined pressurized water reactor safety, mainly within the French nuclear power plant fleet, from the 1970's up to today's Flamanville 3 EPR. Everyone, including current and future generations of engineers, researchers and, more broadly, any citizen interested in nuclear safety issues will find that the book reinforces their knowledge on this important subject, providing an understanding of the fundamentals, to the benefit of nuclear and radiological risk control. The first part of the book presents relatively general fundamental information and concepts that are not specific to pressurized water reactors: the effects of ionizing radiation and the radiological protection system, the organizations involved in nuclear safety in France and their roles, the evolution of regulations, the increasing role of civil society and the international context - two areas that have undergone particularly significant development since the 1990's - and the importance of human and organizational factors for achieving a high level of reliability in nuclear facilities and their operations, which represent complex sociotechnical systems, especially with regard to nuclear power reactors. Subsequent sections, covering design, operation, lessons learned from the three major accidents mentioned above, and emergency preparedness and response, are much more focused on pressurized water reactors, primarily those in the French nuclear power plant fleet, as well as the same type of reactors operated in other countries which have experienced anomalies or events that have provided beneficial operating feedback for the French nuclear power plant fleet. Finally, information concerning the contributions of research and development in nuclear safety, as well as simulation software, are included in the last part of the book