As part of its range of activities, ETSON publishes joint findings on various aspects in nuclear safety and other publications dedicated to the network´s activities or current developments.
Safety Assessment Guide
The Safety Assessment Guide (SAG) provides fundamental recommendations to expertise bodies on reviewing and assessing safety questions raised in nuclear activities. Its main goal is to set down the harmonized principles applied in ETSON organisations to ensure that safety assessments are performed by each ETSON member according to the same lines and can therefore be used with the same confidence by the people concerned. In doing so, ETSON furthers the harmonization of nuclear safety practices in Europe and abroad.
Technical Safety Assessment Guides
Complementary to the SAG, ETSON´s Technical Safety Assessment Guides (TSAG) are dedicated to specific technical issues:
- TSAG – Transients and design basis accident analyses
Safety assessment is a systematic procedure carried out in order to evaluate how the relevant safety requirements are met by the design of the plant. Deterministic accident analyses of both transients and design basis accidents are one of the analytical and essential elements of the safety assessment process. Generally, the deterministic accident analyses are carried out using well established computer tools aiming to confirm that the overall plant design is capable of meeting the acceptance criteria. A full range of operational modes and initiating events has to be considered for these analyses.
Assuming as a prerequisite that the acceptance criteria are appropriate and adequate, this TSAG addresses the review of deterministic safety analyses of both transients and design basis accidents, aiming to verify that the essential physics is correctly identified and modeled and that there are adequate safety margins to cover the remaining uncertainties. The guide also provides guidelines to set up the Safety Evaluation Report, including aspects related to the assessment of computer tools and analysis methodologies.
- TSAG – Deterministic severe accident analyses
Deterministic severe accident analyses are used for various purposes. Those include, for instance, to support of the development of severe accident management (SAM) programmes and respective measures and backfittings. Furthermore, results of respective analyses are used to support probabilistic safety assessments or source term assessments as well as programmes for equipment qualification.
The goal of this document is to provide guidance for reviewers of TSOs to check the compliance of submitted safety analysis with safety requirements (or safety objectives) related to severe accidents. This guide mainly applies to deterministic severe accident analysis of Light Water Reactors.
- TSAG – Event review and precursor analysis
The purpose of event reviews and precursor analyses is to draw lessons from events with safety significance occurring at plants during operation, surveillance and maintenance activities, including deviations from the normal performance of systems or human errors, which may be precursors to severe accidents. Respective analyses of safety-related events are performed by different types of organisations: utilities analyse the events first, afterwards the regulatory bodies and/or its Technical Safety Organisations (TSO) conduct their own review which leads to independent assessments.
The goal of this guide for event review is to provide an approach to deal with all the main issues of events and precursor analyses. It also outlines a synergistic process that makes more effective use of operating experience event information by combining the insights and knowledge gained from both approaches: traditional deterministic event investigation and PSA-based event analyses.
- TSAG – Human and organisational factors in nuclear facilities design and modification processes
This TSAG addresses the review and assessment to be performed by regulatory bodies regarding human and organisational factors (HOF) during design and modifications of nuclear facilities.
Its primary goal is to provide guidance for reviewers/assessors with at least basic knowledge about HOF. This guidance relies as far as possible on practical experience considering safety assessment in the HOF field.
- TSAG – Safety Fluid Systems
This Technical Safety Assessment Guide (TSAG) is intended for/addressed to engineers working in Technical Safety Organisations related to safety authorities regarding nuclear installations and describes the process of performing a safety assessment concerning a (part of a) safety fluid system. This TSAG has the purpose of addressing safety assessments of systems for both new and existing reactors.
The TSAG will take into consideration only fluid systems necessary for design basis accidents (Defense in Depth - DiD level 3 for existing plants or 3a for new plants - see Report "Safety of new NPP designs"; WENRA; March 2013). All safety related auxiliary fluid systems are also included in the scope of this TSAG. Ventilation systems are included as well; these systems share a lot of similarities and make use of the same principles during the assessment process. Fluid systems required in DBA concerning the spent fuel pool are addressed as well.
- TSAG – Environmental Qualification
Equipment needed to fulfil safety functions has to be qualified for the conditions in which it is required. Qualification includes both function and reliability, considering environmental conditions which equipment would be exposed to in the plant, including severe accident conditions. The qualification process, especially for new equipment, shall be completed before plant start-up. In some cases, already installed equipment may be used to face up new situations (for example Design Extension Conditions). In such a case, qualification is either demonstrated by verifying that these situations are covered by already performed qualification tests of justification or by performing a new qualification dedicated to these situations. The methodology for the qualification is strictly the same.
This TSAG deals with Environment Qualification (EQ) in normal, abnormal service conditions, design basis accidents and design extension conditions including severe accidents. For equipment that needs to be qualified to design extension conditions, specific accident profiles covering these conditions shall be defined. This guide primarily applies to nuclear power plants, but may also be applied to other nuclear facilities, such as research reactors.
- TSAG – Pressure Vessel
The Reactor Pressure Vessel (RPV) is one of the most important components in nuclear power plants. It can be the life-limiting component of a nuclear power plant, if its mechanical properties are degraded to such an extent that RPV integrity cannot be proven for all operational and accidental situations of the plant. Moreover, in the frame of the defence-in-depth approach, a failure of the RPV is not assumed in the original design basis of the plants in operation today. This means that there are no measures which could ensure accident mitigation in case of RPV gross failure except for those plants that implemented measures to cope with this failure. Yet, for most plants in operation today, this application of the assumption of break preclusion to the RPV therefore requires ensuring a very low probability of RPV failure by strengthening the first two levels of the defence-in-depth approach. This is performed by defining stringent regulatory requirements in the design, procurement, manufacturing, in-service inspection, surveillance program, and more globally in the structural integrity assessment of the RPV.
Most of the regulatory requirements related to the RPV structural integrity defined in the different ETSON countries are based on similar principles, but their approaches may differ significantly. In the frame of the activities of the ETSON Expert group “Mechanical Systems”, it has been decided to compare regulatory requirements for RPV fracture mechanical assessment in ETSON member states, particularly in Belgium, Czech Republic, France, Finland, Germany, Russia, Slovakia, Switzerland and Ukraine. This TSAG provides a synthesis of this comparison.
Progress and Annual Reports
Since 2010, ETSON has published yearly progress reports (or, from 2018 on, annual reports) to inform interested parties about its achievements and ongoing projects:
|Annual Report 2018||Progress Report 2017||Progress Report 2016|
|Progress Report 2015||Progress Report 2014||Progress Report 2013|
|Progress Report 2012||Progress Report 2011||Progress Report 2010|
Technical and other reports
Complementary to its TSAG series, ETSON also issues reports and other publications on specific issues, mostly referring to current developments or actual events:
From 2001 until 2016, GRS and IRSN published the magazine "EUROSAFE Tribune". Twice a year, this publication provided readers with articles about key issues in the world of nuclear safety and radiological protection. In alternating sequence, the editions of the EUROSAFE Tribune focussed on the respective EUROSAFE Forum´s main subject and on special topics.
All issues are available here: