Investigation of Ageing Effects Using the Probabilistic Safety Assessments - Proceedings of the European Workshop on Probabilistic Safety Assessment

JRC – IE Petten organized with the support of the Kernkraftwerk Gösgen-Däniken, Switzerland, an EC Workshop on Investigation of Ageing Effects using the Probabilistic Safety Assessments. The goal of the workshop was to present and discuss the developed methods and approaches and the results obtained for application of reliability and PSA techniques on evaluation and management of NPP ageing. For the units which have approached the end of initial design lifetime and especially for those which are planning to extend the lifetime, it has to be demonstrated that the plant safety level will remain adequate until the end of operation, and to do that, is necessary to evaluate the effects of ageing phenomena on the plant performance and safety. The workshop contained a general session, dedicated to activities of different organizations in PSA field, and a technical session, focused on the results obtained in application of reliability and PSA techniques on evaluation and management of NPP ageing. Based on the presentations and participants experience, discussions about topics considered interested to be developed further were organized. The arising conclusions are presented.JRC.F.5-Nuclear Reactor Safety Assessmen

Terms of Reference for APSA European Network on Use of PSA for Evaluation of Ageing Effects to the Safety of Energy Facilities. Revision 2

The Terms of Reference specifies the background, objectives, scope, main tasks and organization of European Network on Use of Probabilistic Safety Assessment (PSA) for Evaluation of Ageing Effects to the Safety of Energy Facilities (EC JRC IE APSA Network). The Network was initiated under the JRC FP6/ 7 Institutional Action "Analysis and Management of Nuclear Accidents" (AMA) and is now operated within the framework of the JRC-IE Institutional project "Plant Operation Safety" POS no. 52103. This document updates the JRC-IE report EUR 22645 EN, issued in 2007. The document is prepared in accordance with the requirements of JRC QA Work Instruction "Management of Partnerships and Networks" W400 1.JRC.DDG.F.5-Safety of present nuclear reactor

Qualitative Approach for Selection of Systems Structures and Components to Be Considered in Ageing PSA

This report presents a qualitative approach for selection of Systems, Structures and Components (SSC) sensitive to ageing. The purpose of selection is to model and evaluate SSC ageing effects on the overall NPP safety by applying Probabilistic Safety Assessment tool. The report was prepared by Institute for Nuclear Research, Pitesti, Romania in cooperation with Institute for Energy, EC Joint Research Center, Petten, Netherlands in the frame of EC JRC Ageing PSA Network Task 3 activities. The goal of the work is to demonstrate the feasibility of qualitative assessment in selection of components sensitive for ageing and to develop a viable guideline for selection of components susceptible to ageing. An overview of the available approaches for selection of ageing components was performed, and the methods are briefly presented. Their advantages and disadvantages, as their limitation are also specified. Applicability of the approach for qualitative selection of SSCs susceptible to ageing was demonstrated by a case study which use as an example SSCs of NRI TRIGA research reactor. A list of ageing mechanisms, as their favourable factors for occurrence is provided in appendices of the report.JRC.F.4-Safety of future nuclear reactor

Guideline for Selection of Systems, Structures and Components to be considered in Ageing PSA

The guideline intends to provide a practical approach and to recommend the methods to be used in selection/prioritization of components, systems and structures (SSC) sensitive to ageing and important from risk point of view in operating nuclear power plants. The approach intends to ensure that the selection process will be carried out and documented in a uniform and consistent manner. The methods suitable for selection are briefly presented, and their advantages and disadvantages are specified. A list of generic ageing mechanisms, the factors favorable for their occurrence and some sensitive materials are provided in appendices. In the appendices are presented also the specific approaches and criteria used for SSC prioritization and selection in case studies performed in the frame of Ageing PSA task 3 activities. The guideline was developed in the frame of EC JRC Ageing PSA Network (APSA) activities.JRC.DDG.F.5-Safety of present nuclear reactor

Feasibility Study for Applicability of Ageing PSA Model Results in Risk-informed Decision Process

The aim of this case study was to demonstrate the benefits of using ageing probabilistic safety analysis (PSA) results in risk-informed decision process. First stage of the activities was aimed on the development of dataset which reflects age-dependent reliability behaviour for selected components using plant-specific, VVER specific and generic data. The second part describes the integration process of time-dependent reliability dataset in PSA model, quantification and comparison between aging (APSA) and base case PSA decision making results. Practical insights and conclusions are also presented. The report was prepared by the Nuclear & Radiation Safety Center (NRSC), Yerevan, Armenia, in cooperation with the Institute for Energy and Transport, EC Joint Research Centre, Petten, Netherlands, in the framework of the EC JRC Ageing PSA Network Task 8 activities.JRC.F.5-Nuclear Reactor Safety Assessmen

INVESTIGATING THE RELATION BETWEEN COMMON CAUSE COUPLING FACTORS AND AGEING

Usually, probabilistic safety analyses are using the assumption of the constant component failure rate, and the assumption that the probability associated to common cause failure (CCF) will be constant in time. Still, as ageing phenomena could have some influence on components or systems performances, is probable that it could influence the probability of occurrence of CCFs also. This paper is devoted to investigation of the most important CCFs initiating factors from point of view of relation to ageing phenomena. The connections between CCF potential and ageing phenomena, as the influence of the individual prevention factors against CCF were evaluated. A questionnaire has been developed on this topic and all the inputs provided were summarized, compared and commented. The analysis has not been limited only to the list of negative factors that would increase the CCF potential, it has included also positive factors representing the prevention and correction measures applied with the aim to avoid occurrence and recurrence of CCF events, whether related to ageing or not. Two main topics were discussed: a) the strength of relation between the individual CCF coupling factors (contributing to total CCF potential) and ageing phenomena; b) the effect of CCF prevention measures on the coupling factors versus ageing relation (estimated for those CCF coupling factors that were evaluated as coincident with ageing phenomena, with at least medium level of coincidence).JRC.F.5-Nuclear Reactor Safety Assessmen

Analysis of Common Cause Failures Coupling Factors and Mechanics from Ageing Point of View

The investigation of ageing phenomenon impact on CCF potential was the main goal of Task 5 of the EC JRC Ageing PSA (APSA) Network. This report is devoted to investigation of close links between CCF potential and ageing, and provides expert opinions (based on the questionnaire answers) regarding connection between common cause failure potential and ageing phenomenon, as the influence of the individual prevention factors against CCF. In the questionnaire, two main topics were discussed: -What is the strength of relation between the individual CCF coupling factors (contributing to total CCF potential) and ageing phenomenon? -For those CCF coupling factors, which have been evaluated as coincident with ageing phenomenon (at least medium level of coincidence) - what is the effect of CCF prevention measures on the coupling factor versus ageing relation? A specific color scale was used to specify the strength value of CCF coupling factor and ageing phenomenon relation and to define the strength of potential influence of prevention factor on the strength of link between CCF potential and ageing phenomena. The strength value assigned in the table was commented (reflection in operational experience, assumptions etc.). The strength between CCF coupling factors and ageing and the influence of the individual prevention factors against CCF was evaluated based on available operational experience and expert judgments.JRC.F.5-Nuclear Reactor Safety Assessmen

Evaluation of LOCA Frequency using Alternative Methods

The report presents two different models for derivation of plant specific frequency, in case of Loss of Coolant Accident (LOCA), using specific data from Goesgen NPP, as well as data from the OPDE-database. The first model is using the EPRI methodology of pipe section, and the second model is using the Markov modelling for piping reliability assessment. For both methods, the pipe boundaries are considered to be ASME Class 1 pipes, with diameters between 10 and 750 mm. The information gathered provides valuable insights with respect to Goesgen pipe reliability and can be used for different applications, as for example the evaluation of LOCA or the frequency of internal floods. The information gathered also provides insights with respect to evaluation of the efficiency of the plant-specific ageing management program.JRC.F.5-Nuclear Reactor Safety Assessmen

Analysis of Data related to Ageing of VVER-440 NPP Components

The aim of case study was to demonstrate the applicability of methods for reliability parameters estimation, presented in the guideline (EUR 23954 EN), using the operational data from VVER-440 plants. Two types of calculations were performed, using Excel functions and WINBUGS scripts, to identify the possible trends of data. The study results are useful in revealing the problematic issues connected with use of data guideline (EUR 23954 EN) and for improvement of decision making process based on calculation results. Practical insights, recommendations and limitations are also discussed. The report was prepared by the Nuclear & Radiation Safety Center (NRSC), Yerevan, Armenia in cooperation with the Institute for Energy, EC Joint Research Centre, Petten, Netherlands, in the framework of the EC JRC Ageing PSA Network Task 4 activities.JRC.DDG.F.5-Safety of present nuclear reactor

Ageing Probabilistic Safety Assessment Network - Achievement and Perspectives

This paper presents the main achievements obtained in the frame of Joint Research Centre - Institute for Energy (JRC-IE) institutional project "Use of PSA for Evaluation of Ageing Effects". The project started in 2004, with 14 organizations which were interested in the subject and have their own/ national research program in the area. The participants are highly qualified experts from EU Member State, Switzerland, Russian Federation, Armenia and Korea. The network intends to contribute in the understanding of the impact that ageing phenomena could induce on the plant performances, to promote the use of PSA for ageing management, Long Term Operation activities and for risk-informed decisions, and to disseminate the lessons learned from impact of ageing phenomena in NPP. Future APSA Network works are presented also.JRC.F.5-Safety of present nuclear reactor