Scope and Objectives

History and scope of the network

Despite the accident prevention measures adopted in the nuclear power plants (NPP), some accident scenarios, in very low probability circumstances, may result in severe accidents (SA) with core melting, plant damage and subsequent dispersal of radioactive materials into the environment, thus constituting a hazard for the public health and for the environment. Large progress has been made since the 80’s thanks in particular to the Framework Programmes (FP) of the European Commission, but several issues still need research activities to reduce uncertainties and consolidate SA management (SAM) plans. Facing the reduction, in the first years of the 21st century, of the national budgets on research on SA, it was judged necessary to better coordinate the national efforts to optimise the use of the available expertise and the experimental facilities in order to resolve the remaining issues for enhancing the safety of existing and future NPPs. This led to launch the FP6 and FP7 SARNET projects from 2004 to 2013.

SARNET tackles the fragmentation that exists between the different research national programmes, notably in defining common research programmes and developing common computer tools and methodologies for safety assessment. The network comprises most of the actors involved in SA research in Europe, plus a few non-European important ones (Canada, Korea, India…). A few organizations are covering a wide range of competences though not complete, whereas others are specialized in very specific areas and thus complementarities are developing. The critical mass of competences for performing experiments needed in the SA domain, analysing them, developing models and integrating them into the ASTEC integral computer code, is achieved for most types of NPPs in Europe.


The SARNET/TA2 key objectives are the following:

  • Improving knowledge on severe accidents in order to reduce the uncertainties on the pending issues, thereby enhancing the plant safety
  • Coordinating research resources and expertise available in Europe
  • Preserving the research data and disseminating knowledge

The work in the network consists mainly in:

  • Ranking periodically the priorities of the research programmes, harmonizing and reorienting existing ones and jointly defining new ones when necessary.
  • Performing experiments on the abovementioned issues and jointly analysing their results in order to develop a common understanding of the concerned physical phenomena
  • Developing and validating severe accident codes, in priority the ASTEC integral code which capitalizes in terms of models the knowledge produced in the network
  • Storing all the experimental results in the scientific databases, in priority on the basis of the JRC-IET (EC) STRESA tool
  • Developing educational courses and promoting personnel mobility between the various European organisations.

Network structure

The SARNET/TA2, coordinated by Jean-Pierre Van Dorsselaere (IRSN), is divided in 6 sub-technical areas (STA):

  • 2.1 In-vessel corium/debris coolability (Alexei Miassoedov, KIT)

  • 2.2 Ex-vessel corium interactions & coolability (Christophe Journeau, CEA)

  • 2.3 Containment behaviour, incl. hydrogen explosion risk (Ivo Kljenak, JSI)

  • 2.4 Source term, as released from NPP to the environment (Luis Herranz, CIEMAT)

  • 2.5 Severe accidents linkage to environmental impact and emergency management (François Bréchignac, IRSN)

  • 2.6 Severe accident scenarios (Felice De Rosa, ENEA)

In addition, the activities of dissemination of knowledge are coordinated by Prof. Sandro Paci (University of Pisa).

The TA2 scope has been extended beyond the scope of the SARNET FP7 project to the issues of emergency management and to severe accident impact on environment.

A Management Team, composed of the network coordinator and of the six above STA leaders, plus the coordinator of dissemination of knowledge activities, is entrusted with the day-to-day management of the network. It meets at least twice a year.

Expected results

SARNET will continue to consolidate the sustainable integration of the European severe accident research capacities.

Capitalizing the acquired knowledge in ASTEC and in the experimental database will produce necessary conditions for preserving the knowledge produced by thousands of person-years and disseminating it to a large number of end-users. By fostering collaborative work on developing and validating ASTEC, the role of this code for any kind of water-cooled nuclear power plant will be reinforced. European end-users are currently mostly using integral computer codes developed in the United States, which results in a strong dependence on the US technology. By fostering collaborative work on the ASTEC code, the role of Europe as world leader in this domain is being consolidated.

These network end-products (ASTEC, experimental database) may be used not only for R&D activities but also for applications by industry and safety authorities (or technical safety organizations). In return, the end-products that capitalize the large amount of knowledge acquired in this area will contribute to a better prevention and mitigation of severe accidents in existing and future European NPPs of diverse types, and thus to the improvement of their safety.

Through a periodic review of priorities and co-programming of work amongst organisations, the use of available means and budget will be more efficient. SARNET becomes clearly a reference for severe accident research priorities and impact on national programmes and fund allocations.

Through education and training programmes, SARNET will develop synergies with educational institutions and thus keep attractive the concerned domain of activity for students and young researchers. This will also contribute to enhance and preserve in a sustainable way the European scientific leadership. The network will also provide a wide panel of competencies for supporting the emergence of new nuclear countries.

Associated R&D projects

Several projects have started in the FP7 or H2020 frame as follow-up activities of the SARNET FP6 and FP7 projects. The websites addresses are indicated in the page Favourite links.

CESAM (Code for European Severe Accident Management) in FP7, coordinated by GRS with a strong IRSN involvement between 2013 and 2017, with the objective of ASTEC code enhancement and extension for use in SAM analysis of the nuclear power plants of Generation II-III presently under operation or foreseen in near future in Europe, spent fuel pools included.

PASSAM (Passive and Active Systems on Severe Accident source term Mitigation) in FP7, coordinated by IRSN between 2013 and 2016, mainly consisting of experiments on mitigation existing or innovative systems to reduce potential radioactive atmospheric releases to the environment in case of SA (filtered containment venting systems, sprays, suppression pools, etc.).

SAFEST (Severe Accident Facilities for European Safety Targets) in FP7, led by KIT and starting mid-2014, on the integration of major European research facilities into a pan-European laboratory for severe accident and corium research and to provide its facilities for transnational access.

ALISA (Access to Large Infrastructures for Severe Accidents in Europe and in China) in FP7, led by KIT and starting mid-2014, on the transnational access to large-scale experimental facilities in European and in Chinese research organizations (in-vessel and ex-vessel corium, external vessel cooling, corium properties, containment and hydrogen issues).

ASAMPSA_E (Advanced Safety Assessment Methodologies: Extended PSA) in FP7, led by IRSN, starting in 2014, with the objective to provide best practice guidelines for the identification of situations of low probability external events (such as earthquake and tsunami) with extreme consequences using Level 1-Level 2 PSAs and for the definition of appropriate criteria for decision-making in the European context.

FASTNET (FAST Nuclear Emergency Tools) in H2020, led by IRSN, starting mid-2015, as answer to the H2020 Sept.2014 Call on the Topic NFRP 2 – 2014: “Tool for the fast and reliable prediction of severe accident progression and anticipation of the source term of a nuclear accident”. Its objective is the qualification of a graduated response methodology that integrates several tools and methods to ensure both diagnosis (what is the actual situation in the installation) and prognosis (what may happen in a foreseeable future) of severe accident progression and estimates the consequences on the surrounding population and the environment in any concept of nuclear power plant or Spent Fuel Pool facility implemented in Europe.

IVMR (In-Vessel Melt Retention) in H2020, led by IRSN, with the objective to determine the applicability and technical feasibility of the IVMR strategy to high power reactors, both for existing ones (e.g. VVER 1000 type 320 units) as well as for future reactors of different types (PWR or BWR). The main outcomes of the project will be relevant assumptions and scenarios to estimate the maximum heat load on the vessel wall; improved numerical tools for the analysis of IVMR issues; a methodology and a harmonized view on the IVMR issues at the European level; concepts and technical solutions to maximize the chances of success of IVMR and recommendations on accident Management when applying IVMR strategy.

AIR-SFP (Air Ingress into Spent Fuel Pools), led by IRSN in 2015-2016 in the frame of the NUGENIA+ FP7 project (the latter is coordinated by VTT) addressing the Spent Fuel Pool behaviour in loss of cooling or loss of coolant accidents. Two tasks are performed: to assess more precisely the applicability of severe accident codes for calculation of transients in SFPs in the frame of a benchmark; and to elaborate a roadmap for further R&D on SFP accidents, both on phenomenology and on applicability of codes.

The following other projects are performed in the frame of OECD/NEA/CSNI ( with a clear link with SARNET activities.

STEM This project, led by IRSN and conducted at the IRSN facilities (EPICUR, START) in Cadarache (France) will be completed in 2015. Its main objective was to improve the general evaluation of the source term and to reduce uncertainties on specific phenomena related to the chemistry of iodine and ruthenium fission products which may be major contributors to the radiological consequences. Three main issues were addressed: a) middle-term iodine behaviour in the containment with specific attention to the stability of deposited iodine aerosol particles under radiation; b) short and middle-term iodine-paint interactions under radiation with organic iodides production, c) ruthenium transport chemistry in order to determine the Ru speciation during its transport through the Reactor Cooling System. A follow-up of the STEM project is currently under discussion.

BIP-2 The three-year follow-up project, led by AECL, started in April 2011 and the final report is to be issued in 2015. The project addressed iodine adsorption and desorption on containment painted surfaces under various conditions, and organic iodide formation. The emphasis was to get a more detailed and mechanistic understanding of organic iodide production during irradiation of iodine-loaded paint, and to extrapolate with confidence from small-scale studies to reactor-scale conditions. A follow-up of the BIP-2 project is currently under discussion.

THAI-2 The phase 2 of the Thermal-hydraulics, Hydrogen, Aerosols and Iodine (THAI-2) project, led by GRS, started in 2011. The new experiments are conducted in the THAI facility operated by Becker Technologies GmbH in Germany. The objective of this follow-up project is to address specific water-cooled reactor aerosol and iodine issues, and hydrogen mitigation under accidental conditions. The project will explore open questions concerning: a)  the release of gaseous iodine from a flashing jet and iodine deposition on aerosol particles, and b) hydrogen combustion during spray operation and passive autocatalytic recombiner (PAR) operation in case of extremely low oxygen content. Understanding the respective processes is essential for evaluating the challenges posed by the amount of airborne radioactivity during accidents with core damage (iodine and aerosols) and containment integrity (hydrogen). A follow-up of the THAI2 project is currently under discussion.

HYMERES The main objective of the Hydrogen Mitigation Experiments for Reactor Safety (HYMERES) Project is to improve the understanding of the hydrogen risk phenomenology in containment so as to enhance its modelling. New elements for the experiments in the PANDA (PSI) and MISTRA (CEA) facilities concern: more realistic flows, interaction of safety components (spray, cooler, PAR...), investigations for safety-relevant system behaviour related to diverse NPPs.

BSAF The Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF), led by Japan, started in 2012. It intends to improve severe accident codes, and to analyse accident progression and current core status in details for preparation of fuel debris removal as a part of the R&D projects for the mid- to long-term response for decommissioning units 1 to 4. The first phase focused on the analysis of the in- and ex-vessel behaviour of corium. A second phase has started mid-2015 to analyse the nehaviour of radioactive releases.