Last update on July 2016
Advanced Safety Assessment Methodologies:
Level 2 Probabilistic Safety Assessment
ASAMPSA2 (Advanced Safety Assessment Methodologies: Level 2 Probabilistic Safety Assessment) was a three-year project launched on January 1, 2008 within the scope of the European Union's 7th R&D Framework Program. The project aimed to establish best-practice methodological guidelines for conducting Level 2 Probabilistic Safety Assessments (Level 2 PSAs). A draft version of theses guidelines was completed in November 2010 and submitted to over 100 organizations in EU and OECD member states as part of an extensive external review process. The results of this review were discussed in an international workshop held in Espoo (Finland) from March 7 to 9, 2011. Participants stressed the quality and detail of these draft guidelines and formulated a number of proposals for improvement. The workshop also served to discuss possible future European projects in this field, such as the reinforcement of Level 2 PSA methods for assessing external hazards or the application of such methods for conducting an in-depth assessment of the robustness of existing procedures for certain reactors. The final guidelines, divided in 3 volumes, are now avalaible.
Coordinated by the IRSN, the ASAMPSA2 project was composed of 21 organizations from 12 European countries involved in nuclear safety-related activities (operators, service providers, safety authorities, manufacturers, research organizations). Given the significant inconsistencies currently existing at the European level, these guidelines serve to harmonize the practical implementation of Level 2 PSA methodologies and the integration of Level 2 PSA results into the overall safety assessment process for nuclear power plants. The team of experts in charge of the project made use of their previous experience and from international cooperation networks, particularly the SARNET European excellence network.
The methodologies described in the guidelines are mainly intended for nuclear power plants currently operating in Europe, but the possibility of applying them to next-generation reactors (Gen III and Gen IV) is also considered. In addition to considering methodological aspects, the ASAMPA2 project also served to identify some R&D areas requiring the implementation of severe accident assessment actions.
The recent accident at the Fukushima Daiichi nuclear power plant (March 11, 2011) has stressed the relevance of European efforts in this field. The participation of ASAMPSA2 project partners in the studies conducted after the accident has led to a postponement of the project completion. A final version of the guidelines, taking into account the results of the external review, has been published in April 2013.
The principal objectives of the ASAMPSA2 project were to:
- identify and review the current needs of Level 2 PSA end users (i.e. operators, plant designers and safety authorities) not addressed in existing guidelines,
- establish a formal set of best-practice guidelines for the development and application of Level 2 PSAs, as a supplement to existing guidelines, proposing two possible levels of detail: simplified or detailed (detailed Level 2 PSAs will meet all applicable requirements in terms of realism, consideration of uncertainties or operational system modeling),
- contribute to the harmonization of European practices in this field so as to ensure a more credible application of Level 2 PSA results,
- distribute these best practice guidelines among Level 2 PSA end users.
Two working groups have been established:
a cross-functional end user workgroup composed of representatives of operators, plant designers, technical safety organizations and safety authorities,
a technical workgroup composed of experts from organizations specialized in the development of Level 2 PSAs.
These workgroups are responsible for the completion of five work packages.
The first group is responsible for work package 1:
- WP1: definition of end-user requirements and verification of consistency between proposed guidelines and expressed requirements.
The second group is responsible for work packages 2, 3 and 4:
Work packages 2 and 3 are carried out in parallel and in close cooperation.
Work package 5 involves cross-functional activities:
The project was completed in three main phases:
Preparation of guidelines (scope of application, content and methodologies, presentation of results) (WP2 and WP3).
Application to Gen IV reactors (WP4): sodium-cooled fast reactors (SFRs), gas-cooled fast reactors (GFRs), very-high-temperature reactors (VHTRs) and lead-cooled fast reactors (LFRs).
The main contribution of the project was to reduce the current lack of consistency among European practices for conducting Level 2 PSAs (despite the existence of guidelines such as those published by the IAEA).
The ASAMPSA2 project has also contributed to the harmonization of current practices by ensuring a higher degree of confidence in the preparation and use of Level 2 PSAs and a more exhaustive identification of severe accident-specific research requirements for both existing and future reactors.
It allowed, after the accident of Fukushima, the emergence of the ASAMPSA_E project (www.asampsa.eu) on methods to extend the scope covered by existing Level 1 and L2 PSA (events such as earthquake, flooding, lightning, extreme weather conditions, aircraft crash and man-made hazards,) and on the role of extended PSA in the overall safety approach (defense in depth principles, design extension conditions, treatment of rare events with extreme consequences, risk-informed decision-making…).