[en] In many real systems, failures occurring to the components, control failures and human interventions often interact with the physical system evolution in such a way that a simple reliability analysis, de-coupled from process dynamics, is very difficult or even impossible. In the last ten years many dynamic reliability approaches have been proposed to properly assess the reliability of these systems characterized by dynamic interactions. The DYLAM methodology, now implemented in its latest version, DYLAM-3, offers a powerful tool for integrating deterministic and failure events. This paper describes the main features of the DYLAM-3 code with reference to the classic fault-tree and event-tree techniques. Some aspects connected to the practical problems underlying dynamic event-trees are also discussed. A simple system, already analyzed with other dynamic methods is used as a reference for the numerical applications. The same system is also studied with a time-dependent fault-tree approach in order to show some features of dynamic methods vs classical techniques. Examples including stochastic failures, without and with repair, failures on demand and time dependent failure rates give an extensive overview of DYLAM-3 capabilities

[en] This paper illustrates a method for efficiently performing multiparametric sensitivity analyses of the reliability model of a given system. These analyses are of great importance for the identification of critical components in highly hazardous plants, such as the nuclear or chemical ones, thus providing significant insights for their risk-based design and management. The technique used to quantify the importance of a component parameter with respect to the system model is based on a classical decomposition of the variance. When the model of the system is realistically complicated (e.g. by aging, stand-by, maintenance, etc.), its analytical evaluation soon becomes impractical and one is better off resorting to Monte Carlo simulation techniques which, however, could be computationally burdensome. Therefore, since the variance decomposition method requires a large number of system evaluations, each one to be performed by Monte Carlo, the need arises for possibly substituting the Monte Carlo simulation model with a fast, approximated, algorithm. Here we investigate an approach which makes use of neural networks appropriately trained on the results of a Monte Carlo system reliability/availability evaluation to quickly provide with reasonable approximation, the values of the quantities of interest for the sensitivity analyses. The work was a joint effort between the Department of Nuclear Engineering of the Polytechnic of Milan, Italy, and the Institute for Systems, Informatics and Safety, Nuclear Safety Unit of the Joint Research Centre in Ispra, Italy which sponsored the project

[en] PRPP Working Group Objectives: • Facilitate introduction of PRPP features into the design process at the earliest possible stage of concept development. → PRPP by design: • Assure that PRPP results are an aid to informing decisions by policy makers in areas involving safety, economics, sustainability, and related institutional and legal issues. “Generation IV nuclear energy systems will increase the assurance that they are a very unattractive and the least desirable route for diversion or theft of weapons-usable materials, and provide increased physical protection against acts of terrorism.”

[en] The EC-JRC International Workshop on Promotion of Technical Harmonisation on Risk-Based Decision Making, held at Stresa and Ispra, Italy, 22-25 May 2000, was an experts meeting to discuss the possible need of developing an internationally accepted generic 'standard' for risk-based decision making.This paper briefly describes the workshop background, its organisation and summarises its main results and conclusions; it reflects the personal opinions of the authors and in no way commits the European Commission. (author)

[en] This paper discusses the main findings and results obtained during the phase 2 of the Benchmark Exercise on Expert Judgment Techniques (BE-EJTs) in PSA Level 2. Phase 2 was devoted to the assessment of the probability of hydrogen deflagration and detonation in a generic evolutionary pressurized water reactor. (author)

[en] This paper discusses the numerical results obtained in the phase 1 of the benchmark exercise on Expert Judgement (EJ) techniques in PSA level 2, which was devoted to forecasting a fuel coolant-interaction phenomenology. A detailed analysis and comparison of structured and unstructured EJ results have been carried out on the basis of pre-defined metrics, i.e. surprise indexes and Matheson-Winkler scores. The results of the comparison are here presented and commented. (author)

[en] Within its State Level Concept (SLC), the International Atomic Energy Agency (IAEA) envisions a State Level Approach (SLA) for safeguards implementation that considers, inter alia, a State’s nuclear and nuclear-related activities and capabilities as a whole when developing an annual implementation plan. Based on the assessed nuclear fuel cycle and related capabilities of a State, Acquisition Path Analysis (APA) identifies, characterizes, and prioritizes plausible routes for acquiring weapons-usable material to aid in safeguards implementation planning. A review of proposed APA methods and historical evidence indicates that assessments of pathway completion time can be fraught with uncertainty and subject to bias, potentially undermining safeguards effectiveness and efficiency. Based on considerations of theory and evidence, a number of methodological insights are identified to support consistent implementation and ongoing APA development. The use of algorithms to support APA and SLA processes in lieu of human judgement is a contentious issue requiring an evidence- based assessment and is also briefly discussed. This paper captures concepts derived primarily from open sources of information, including publications, presentations, and workshops on on-going APA development by the IAEA and various Member States Support Programs (MSSP) as well as relevant work found in the open literature. While implementation of the SLA has begun for a number of States, these SLAs are being updated and developed for other States. In light of these ongoing developments, the topics covered here should be considered a snapshot in time that does not reflect finished products and does not necessarily reflect official views.

[en] The Generation 4. International Forum (GIF) was initiated in 2000 and formally chartered in mid 2001. It was set-up as an international collective representing the governments of ten Countries (Argentina, Brazil, Canada, France, Japan, the Republic of Korea, the Republic of South Africa, Switzerland, the United Kingdom and the United States) strongly involved in the deployment and development of nuclear technology for energy production. The European Atomic Energy Community (EURATOM), represented by the European Commission, signed the GIF charter on July 30, 2003. The People's Republic of China and the Russian Federation signed the GIF charter in November 2006. The Technology Goals for Generation 4. nuclear energy systems, developed during the Road map project, highlight Proliferation Resistance and Physical Protection (PRPP) as one of the four goal areas for these technologies, along with Sustainability, Safety and Reliability, and Economics. On the basis of these four goal areas an evaluation methodology was developed which contributed to identify the six nuclear energy systems (NES) options currently under consideration by GIF. The Generation 4. Road map recommended the development of a comprehensive evaluation methodology to assess PRPP of Generation 4. nuclear energy systems. Accordingly the PRPP Expert Group was formed and tasked by the GIF in December 2002 to develop an improved evaluation methodology on the basis of the Road map's recommendation. The group includes members of the GIF and representatives from the IAEA. The methodology is organised as a progressive approach applying alternative methods at different levels of thoroughness as more design information becomes available and research improves the depth of technical knowledge. To date, the overall framework of the methodology is considered rather accepted and stable; the methodology was advanced with a development case study and has been tested though a demonstration case study. This paper provides an updated overview of the methodology approach developed by the PRPP Expert Group. The paper also highlights some of the achievements and the lessons learned during the demonstration case study carried out in 2005-2006, in which different techniques have been applied for the implementation of the PRPP evaluation framework. Finally the paper presents some of the ongoing activities and future directions for the activity of the group.

[en] State Evaluation Groups in the IAEA Department of Safeguards analyse safeguards-relevant open source information on States’ nuclear-related industrial capabilities, including the nuclear-related equipment and materials they can make use of either through indigenous manufacture or import. This analysis is performed in the State evaluation process for States with comprehensive safeguards agreements. Open source trade statistics can provide insights into the global trade flows of nuclear-related equipment and materials, and the underlying industrial capabilities of States as possible users or manufacturers of such goods. This paper describes preliminary results of the collaborative work between the IAEA and the Joint Research Centre of the European Commission on the development and application of visualization tools to open source trade statistics to support the nuclear related industrial capability assessment in the State evaluation process. Methods for statistical trade data analysis, including the Revealed Comparative Advantage index, were explored to determine the relative strength of States as exporters or importers of classes of products which are considered to be of relevance to the assessment of States’ nuclear-related industrial infrastructure and capabilities. (author)

[en] The collaborative project for a European Sodium Fast Reactor (CP‑ESFR) is an international project where 25 European partners developed Research & Development solutions and concepts for a European sodium fast reactor. The project was funded by the 7. European Union Framework Programme and covered topics such as the reactor architectures and components, the fuel, the fuel element and the fuel cycle, and the safety concepts. Within sub‑project 3, dedicated to safety, a task addressed proliferation resistance considerations. The Generation IV International Forum (GIF) Proliferation Resistance and Physical Protection (PR and PP) Evaluation Methodology has been selected as the general framework for this work, complemented by punctual aspects of the IAEA‑INPRO Proliferation Resistance methodology and other literature studies - in particular for material type characterization. The activity has been carried out taking the GIF PR and PP Evaluation Methodology and its Addendum as the general guideline for identifying potential nuclear material diversion targets. The targets proliferation attractiveness has been analyzed in terms of the suitability of the targets’ nuclear material as the basis for its use in nuclear explosives. To this aim the PR and PP Fissile Material Type measure was supplemented by other literature studies, whose related metrics have been applied to the nuclear material items present in the considered core alternatives. This paper will firstly summarize the main ESFR design aspects relevant for PR following the structure of the GIF PR and PP White Paper template. An analysis on proliferation targets is then discussed, with emphasis on their characterization from a nuclear material point of view. Finally, a high‑level ESFR PR analysis according to the four main proliferation strategies identified by the GIF PR and PP Evaluation Methodology (concealed diversion, concealed misuse, breakout, clandestine production in clandestine facilities) is presented.