The SARNET2 (severe accidents Research NETwork of Excellence) project started in April 2009 for 4 years in the 7th Framework Programme (FP7) of the European Commission (EC), following a similar first project in FP6. Forty-seven organisations from 24 countries network their capacities of research in the severe accident (SA) field inside SARNET to resolve the most important remaining uncertainties and safety issues on SA in water-cooled nuclear power plants (NPPs). The network includes a large majority of the European actors involved in SA research plus a few non-European relevant ones. The “Education and Training” programme in SARNET is a series of actions foreseen in this network for the “spreading of excellence.” It is focused on raising the competence level of Master and Ph.D. students and young researchers engaged in SA research and on organizing information/training courses for NPP staff or regulatory authorities (but also for researchers) interested in SA management procedures.
Despite the accident prevention measures adopted in modern NPPs, some accident scenarios, in very low probability circumstances, may result in a SA, as shown in the accident that occurred at the Fukushima Daiichi NPP in March 2011, with nuclear fuel melting and dispersal of radioactive materials into the external environment, thus constituting a hazard for the public health and for the environment. Significant progress has been achieved since the 1980s in the understanding of a SA progress, thanks in particular to the several research actions carried out inside the different EC FPs, but several “open issues” still need further research activities to reduce uncertainties and consolidate SA management plans [
Facing the increasing reduction of the national budgets on SA researches, in 2003 EC judged necessary a better coordination of the single national efforts in this field to preserve and optimise the use of the available expertise and of the experimental facilities, in order to resolve the remaining “open issues” for enhancing the safety of existing and future NPPs. In April 2004, 51 worldwide organisations involved in R&D on SA, including research organisations, safety authorities, technical safety organisations (TSO), industries, utilities, and universities, decided to network together in SARNET, in the framework of the EC FP6, linking their capacities of research in the SA area in a consolidated manner [ development of education courses on SA for students and researchers, and training courses for specialists, promotion of personnel mobility amongst various European organisations, organisation of large international conferences on SA researches.
This education and training programme has been set up to disseminate the excellence and knowledge in the SA area, including out of the SARNET2 network perimeter. It is intended to be an in-depth treatment so that the university students and researchers will be able to (a) understand and (b) develop the methodology in the topics further and (c) use analysis tools more effectively. In particular, the mobility programme under which students (including students from European universities out of the SARNET2 perimeter) and researchers will be able to go into different laboratories of SARNET2 partners for training will complete this education and training programme to develop a common safety culture throughout Europe. Links with the ENEN (European Nuclear Education Network) association have been also strengthened, ENEN being a nonprofit international organisation established on September 2003 under the French Law of 1901 with the mission of the preservation and further development of expertise in the nuclear fields by higher education and training.
Forty-seven partners from Europe, Canada, India, South Korea, United States, and Japan participate currently in SARNET with an overall manpower that represents about 40 persons per year (230 researchers and more than 20 Ph.D. students are involved in the network). This excellence network has been defined in order to optimize the use of the available research budget and to constitute a sustainable consortium in which common research programmes in the SA area and a common SA code (ASTEC) are developed. The ASTEC integral code [
In the SARNET network structure (Figure integrating activities, aiming at the management of the network and at strengthening links among the partner organisations (WP1 on management, WP3 on information systems and WP4 on ASTEC code), joint research activities (from WP5 to WP8), spreading of excellence in WP2 (analysed in detail in the following).
Structure of the SARNET network.
About 320 papers related to SARNET activities in the last 7 years have been presented in conferences or published in scientific journals. The dissemination of internal and public information is also done through periodic open newsletters, two websites (the public one and the restricted one) and the participation of the members to public events. After the mid-term of the project, the paper in [
IRSN and German Gesellschaft für Anlagen und Reaktorsicherheit mbH (GRS) jointly develop the ASTEC code to describe the complete evolution of a SA in a water-cooled reactor, including the behaviour of engineered safety systems and procedures used in SA management (SAM). The series of code versions V2 aims at covering all European NPPs and the new Gen. III light water reactor (LWR) designs; it can simulate the EPR (European pressurised reactor), especially its external core-catcher, and it includes the advanced core degradation models of the IRSN ICARE2 mechanistic code.
Both organisations also assure the code maintenance and the support to the code users, notably through annual ASTEC Users’ Club meetings. In fact, twenty-eight organisations actively collaborate on the development and in the assessment of the successive ASTEC versions. The code assessment activity mainly consists in covering a broad matrix of reactor applications, aiming at the most important SA scenarios for 4 types of water reactors (PWR, BWR, VVER, and CANDU) present in Europe. In complement to these reactor applications, ASTEC assessment continues through calculations of a wide range of experiments in different SA areas, such as the Phébus FP experiments [
A public website (
One of the main SARNET goals is also to collect and preserve, for future utilizations, the large quantity of today’s available SA experimental data, in order to ensure their preservation, exchange, and processing, including all the related documentation. The data collected inside DATANET are both previous experimental data that partners are voluntary willing to share and all new experimental data produced within SARNET since 2004. DATANET is actually based on the STRESA tool [
One of the achievements of SARNET consisted in obtaining a European consensus on six high priority issues on which research was still considered as necessary. These six open safety issues, selected at the beginning of the SARNET2 project, are analysed inside the WPs 5 to 8: core coolability during reflooding and debris cooling—WP5, ex-vessel melt pool configuration during molten corium concrete interaction (MCCI), ex-vessel corium coolability by top flooding—WP6, melt relocation into water, ex-vessel fuel coolant interaction (FCI)—WP7, hydrogen mixing and combustion in containment—WP7, oxidising impact on source term—WP8, iodine chemistry in reactor coolant system (RCS) and in containment—WP8.
The experimental efforts carried out in SARNET2 are mainly devoted to two of these open issues, for which a real progress toward the “closure” of the issue itself is expected: “corium/debris coolability” and MCCI. For all these six issues, the same method is adopted: review and selection of available relevant experiments, contribution to the definition of new test matrices, synthesis of the interpretation of experimental data, benchmark exercises among available codes, review of models, and synthesis and proposals of new or improved models to be implemented inside ASTEC.
The ranking of R&D priorities has been recently reviewed and updated to take into account the Fukushima-Daiichi accident that took place in Japan in March 2011. No strong evolution of priorities was concluded, but a few new subjects were identified where the efforts must be increased in the next years.
Indeed a key integration aspect of the SARNET network is the setup of the “technical circles,” each covering a specific detailed topic. These technical circles, experimented with success in the recent past for the PHEBUS FP experimental programme [
The major motivation is to solve the remaining uncertainties on the possibility of cooling structures and materials during a SA sequence, either in the core or the vessel bottom head or in the reactor cavity, in order to limit the accident progression. This could be achieved by water injection either by ensuring corium retention within the vessel or at least slowing down the corium progression and limiting the flow rates of corium release into the reactor cavity. These issues are covered within SAM for current reactors and also within the scope of the design and safety evaluation of future reactors. The following 3 key situations and processes are analysed inside this WP5: reflooding and coolability of a degraded core, remelting of debris, melt pool formation, and coolability, ex-vessel debris formation and coolability.
The addressed main situation is the reactor pit initially dry but with the possibility of water injection later during MCCI. The work programme is complementary with the OECD/NEA (Nuclear Energy Agency) MCCI project that finished in 2011 [
The considered issue is the threat to the containment integrity due to two types of highly energetic phenomena: steam explosion and hydrogen combustion. Steam explosion may be caused by ex-vessel FCI due to a vessel failure and pouring of the corium in the flooded reactor cavity. Hydrogen combustion may be caused by ignition of a gas mixture with high local hydrogen concentrations, which may be due to the imperfect mixing of the containment atmosphere. Phenomena, as the containment atmosphere stratification, influencing these threats are considered as well.
Several benchmarks were launched inside this WP7, involving simulation codes on different physical phenomena or safety systems influencing the behaviour of the containment atmosphere, such as containment sprays [
The overall objective is to reduce the uncertainties associated with calculating the potential releases of radiotoxic fission products to the external environment. WP8 activities are concentrated on iodine and ruthenium, given their high radio-toxicity, noting that the ruthenium release is enhanced in oxidising atmospheres, such as those that may follow air ingress into the RCS. The research treats the transport of these elements through the RCS and their behaviour in the containment. Of particular importance is the prediction of volatile iodine and ruthenium species in the containment, forms that are hard to remove by containment sprays or by filtration while the venting of the containment system is actuated.
Full advantage is taken of cooperation with international programmes such as Phébus FP, International Source Term Programme (ISTP) [
The “Education and Training” Programme, included in the WP2 “spreading of excellence,” is focusing on the following. Raising the competence level of the European university students (Master and Ph.D.) and young researchers engaged in SA research. Towards this purpose, in the streamline of what was done in the SARNET FP6 project, new Organisation of Publication at the beginning of 2012 of the SARNET text book on SA phenomenology [
Other “spreading of excellence” activities foreseen inside this WP2 are the organisation of periodic European Review Meetings on Severe Accident Research (ERMSAR Conferences) and the mobility programme (MOB), under which university students and young researchers can go to internship programmes. These particular activities will be illustrated in the following part of the present paper.
The SARNET
During the previous SARNET FP6 project, three short courses (1 week) on the different aspects of SA research were organized, by different partners, with a mixed content (not only phenomenology but also SAM and SA codes): SA phenomenology, including some description of the SAM, SA progression (analysis, data and uncertainties) to give the order of magnitude of physical phenomena occurring during a SA progression to researchers and engineers working in industry and regulatory organisations, nuclear reactor SA analysis: application and management guidelines, focused more on SA methodology (models, codes), analyses, and SAM.
The first educational SARNET2
Nationalities of the participants in the Pisa 2011 course.
An evaluation form was distributed during the last days of the course to the participants to analyse the course and its impact. The evaluation was generally made on a scale from 1 (very bad) to 5 (very good). The evaluation of the general organisation of the course was very good for the overall mark: 4.32/5. Participants have not expressed a main field of interest for reactor applications, with a quite equilibrated distribution of this interest between Gen. II and Gen. III reactor design and the lectures had an average mark of 3.86/5, with no BAD or VERY BAD marks. Finally, it can be stated that the course met very well the participant expectations in terms of personal objectives in the field of SA as can be highlighted from the distribution of answers at the main question
The second SARNET two-day course was an information and training one. It was entitled historical overview including a review of TMI, Chernobyl, and—above all—Fukushima accidents, short introduction to the SA phenomenology, overview of the main SA codes (in priority ASTEC and MELCOR), severe Accident Management Guidelines, backfitting of Gen. II NPP and SA mitigation for Gen III plants, radiological consequences to the environment and to the public resulting from a SA.
Lectures have been given by 10 international experts from major nuclear institutes, industries, and universities working on the SA topic. As expected, the participation at this course was good but lower respect to the Pisa course, considering the particular high level target of the audience, with 32 participants but from 11 worldwide countries (see Figure
Nationalities of the participants in the KIT 2012 course.
The next SARNET course will be again an educational one-week course, based on the skeleton of the Pisa one, following the strong requests to repeat this kind of phenomenological course received from different worldwide organisations after the Fukushima accident.
The Mobility Programme (MOB) aims at training young researchers and students through a delegation towards SARNET research teams, in order to enhance the exchanges and the dissemination of knowledge on SA area. In this MOB programme, the long-term goal is to build and strengthen teams which would engage together in a certain activity of the excellence network. A total of 33 mobility actions (with an average duration of 3 months) were completed at the end of the SARNET FP6 project, where most of the delegates were from Eastern Europe countries (as defined in the EU EuroVoc multilingual thesaurus) going to laboratories and universities in Western Europe countries and a large fraction of the delegates were women. The dominant area of training was on the use of the ASTEC code.
In SARNET2 FP7 an increased financial support covering partially the delegation costs (maximum of 2000€/month) is provided. To apply for mobility support, the following conditions shall be fulfilled: organisations shall be SARNET members (or only the hosting one for the delegation of an university master/Ph.D. students), the work to be performed during the delegation period shall be relevant to SARNET objectives and be part of the JPA, the delegation shall contribute to the transfer of knowledge/know-how. The allocation of funds is subject to the final delivery of an open delegation report describing the main technical achievements. The number of these mobility actions is one of the several integration indicators defined in order to assess the progress of the SARNET2 FP7 project and the success of the network integration: in total 21 mobility actions have been authorized, with the distribution among the different WPs reported in Figure
Distribution of the SARNET2 MOB actions.
Distribution of gender for MOB actions.
For the success of this SARNET MOB programme, strong partners’ efforts were needed to highlight research projects which could be of interest to young researchers or students and to disseminate internally and externally the understanding of the benefits of this MOB program. In this context an attractive idea has been to arrange, for the university delegates, to perform a master thesis and/or to take courses in SA technology in the EMSNE framework, funding the master thesis stages in the SA field to be performed to obtain the 20 ECTS necessary for the EMSNE achievement.
Five ERMSAR (European Review Meetings on Severe Accident Research) conferences have been organized successively in France, Germany (twice), Bulgaria, and Italy as an exchange forum for the whole international SA community. The proceedings of these ERMSAR Conferences are available for download on the SARNET2 public website.
The 4th ERMSAR conference was hosted by ENEA in Bologna (Italy) on May 11-12, 2010. It gathered 98 participants from 24 different nationalities (8 non-EC countries and 15 EC ones). The SARNET partners presented papers on their joint work, including some first conclusions of the work done in the first period.
The latest 5th ERMSAR conference was the first one fully open to the international community. It has been hosted by GRS in Cologne (Germany) on 21–23 March 2012, gathering 157 participants with 52 presented papers, not only by SARNET partners. The participants came from 60 organisations and 27 countries (42 of them were coming from non-SARNET partners). This seminar aimed at presenting the current status of R&D on SAs both in Europe and elsewhere, as an “open conference.” Therefore, beside the presentations of the current work by SARNET members in the network JPAs, non-SARNET organisations were invited to contribute through papers and presentations to the seminar or the SARNET members were also able to present SA individual work conducted outside the JPAs. The four previous ERMSAR conferences provided insights on the SARNET network activities and in particular on the SA research priorities established in 2008. On the contrary, the global objective of this 5th seminar has been to present the recent progress of international knowledge on SAs, of course including the work done within the SARNET network in the last two years. It was also an opportunity to discuss future R&D priorities on SAs and, in particular, how the feedback of the Fukushima accident can be taken into account in planning the new research needs.
The final ERMSAR 6th Conference will present all the results of the whole SARNET project.
After a first phase of four and a half years, the SARNET network of excellence continues from April 2009 for four years more on the different SA research lines. SARNET aims both at solving the latest “open” issues in this field for current NPPs safety and at consolidating the sustainable integration of the European SA research capacities. Efforts have also continued on the preservation and the transfer of knowledge to younger generations through the different “spreading of excellence” activities, including the publication of the SA text book, the organisation of the education and training courses, and other different actions.
The work done on the ASTEC code assessment and improvements will reinforce ASTEC position of European reference SA code. It will allow preservation of knowledge produced by thousands of person-years of R&D and dissemination to end-users.
Links with OECD/NEA and other programmes co-funded by the EC will be maintained and reinforced, in particular with ENEN association for education and training courses for students and young researchers, and with NUGENIA (a non-profit-making association dedicated to the research and development of nuclear fission technologies, with a focus on Gen. II and III NPPs, gathering stakeholders from industry, research, safety organisations, and academia and committed to develop joint R&D projects in this field) and SNETP (the European stakeholder forum for nuclear technology). Finally, in order to keep the competence in SA and SAM alive after the SARNET2’s end in 2013, a self-sustaining entity in the field of SA research is under construction in close links with NUGENIA.
The authors thank the European Commission for funding the SARNET network in FP7 (Project SARNET2 no. 231747 in the area “Nuclear Fission and Radiation Protection”).