Identification of European experimental facilities for severe accident research within EU SEAKNOT-project: Analysis and mapping

EPJ Nuclear Sci. Technol. 11, 75 (2025) c V.H. Sanchez-Espinoza et al., Published by EDP Sciences, 2025 https://doi.org/10.1051/epjn/2025071 Available online at: https://www.epj-n.org Identification of European experimental facilities for severe accident research within EU SEAKNOT-project: Analysis and mapping Victor Hugo Sanchez-Espinoza1,∗,?, Pascal Piluso2,? , and Luis Enrique Herranz3,? 1Karlsruhe Institute of Technology (KIT), Hermann-vom-Helmholtz-Platz-1, Eggenstein-Leopoldshafen 76244, Germany 2French Alternative Energies & Atomic Energy Commission (CEA), IRESNE, Centre de Cadarache, Bat.219-D, St Paul Lez Durance cedex 13108, France 3Centro de Investigaciones Energ´eticas, Medioambientales y Tecnologicas (CIEMAT), Nuclear Safety Research Unit, Department of Energy, Madrid 28040, Spain Received: 10 June 2025 / Received in final form: 20 October 2025 / Accepted: 20 October 2025 Abstract. Experimental facilities play a central role in reactor safety research for both design basis and severe accidents (SA). They are key to demonstrate the effectiveness and appropriateness of specific safety features of reactor designs and providing data for the validation of different models implemented in numerical tools used for safety demonstration. Hence, a well-designed and equipped experimental infrastructures in Europe is a fundamental pillar of European roadmap on reactor safety research. One objective of the EU SEAKNOT (Severe Accident research and KNOwledge management) project, is the analysis and mapping of European severe accident research facilities currently under operation. The responses to a questionnaire sent to European institutions were evaluated and the information collected about each facility was synthesized covering different issues such as age, design features, main phenomena addressed by latest research programs, including advanced technologies like Advanced Technology Fuels (ATFs) and Small Modular Reactors (SMRs). The extensive review of the collected information allowed the identification of critical conditions (human resources; preservation and enhancement of experimental competences, etc. that might jeopardize the current and forthcoming European experimental capabilities for severe accident research, according to the Severe Accident roadmap that is being built in SEAKNOT. This paper describes the methodology and major outcomes of this analysis. 1 Introduction Experimental research is a key pillar to enhance knowledge and perform code validation. In addition, the construction and operation of experimental facilities equipped with state-of-the-art measurement devices to catch the physical phenomena of interest may be in some cases very costly. Nevertheless, key experimental investigations are mandatory in nuclear engineering which is highly regulated to assure robust safety features at high standards in the safe design and operation of nuclear reactors. The safety demonstration in the frame of a licensing process or during the regular supervision of the operation is based on numerical tools validated for the reactor design of interest and it is complemented by dedicated experiments. In view of the increased interest on the deployment of Generation 3 and 3+ Light Water Reactors (LWR) and of water ∗e-mail: [email protected] ?These authors contributed equally to this work. cooled (WC) Small Modular Reactors (SMR) in the EU [1] and worldwide [2], it is of great interest to do a systematic screening of the experimental research programs across Europe, specifically dedicated to severe accident phenomena, nowadays running. Based on such studies, strategic recommendations to the stakeholders can be done to keep high level of knowledge needed to assess the safety features of any reactor design going to be built in the EU in the next years. In the EU, new initiatives were started e.g., in the European User Facility Network (OFFERR) with the goal to optimize the use of existing experimental facilities and open opportunities for research groups without experimental infrastructure to take profit of existing ones and to take part or even perform experiments according to their needs [3]. Hence, the Horizon Europe SEAKNOT project [4,5] that started in 2022 aims to contribute to the knowledge preservation and dissemination about severe accident research in Europe. To achieve these goals, the following objectives are defined: (1) perform a critical 2 V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) Table 1. Number of emails-requests, answers and facilities. Category Number of e-mails Number of answers/ sent out number of facilities Test facilities in SEAKNOT-Partners involved in WP3 20 20/52 Test facilities in SEAKNOT-Partners not involved in WP3 9 9/5 Test facilities in institutions of EU-Countries partners of SEAKNOT but not beneficiaries of SEAKNOT 12 2/1 Test facilities in institutions of EU-Countries not partners of SEAKNOT 12 4/1 analysis of the existing knowledge on severe accidents, (2) identify the needs for future experimental research required to understand the severe accident progression required for the optimization of mitigative measures aimed to minimize the radiological consequence of core meltdown accidents and (3) disseminate and improve the knowledge of young researchers on reactor safety regarding both analytical and experimental investigations on relevant severe accident domains. These goals can be translated in the following specific objectives: –Elaborate a Phenomena Identification Ranking Table (PIRT) on severe accidents considering the available EU-capabilities on severe accident experimental research (Work Package 1), –Elaborate a validation data base directory by developing a comprehensive mapping of the existing and future experimental European activity (2023–2030) (Work Package 2), –Build a Severe Accident Infrastructure NETwork (SAINET) of the European research infrastructure on severe accident for the time horizon 2023–2030 and identify the severe accident phenomena addressed including ATFs, mitigation actions, and accidentresistant instrumentation including SMRs (Work Package 3), and –Promote mutually beneficial collaborations between the experimental facilities and the various European partners such as universities, regulatory bodies, and industry (Work Package 4). The Work Package 3 is focused on two tasks: – Mapping of Severe Accident Experimental Facilities (MAPEX): The goal here is to identify and list the experimental facilities devoted to severe accident research still in activity inside Europe (within SEAKNOT-partners, EU-institutions in countries partners of SEAKNOT, and in EU-institutions not participating in SEAKNOT). – Establishing a Severe Accident Infrastructure NETwork (SAINET): The goal here is to build SAINET infrastructure to gather main players in Europe on the field of severe accident research based on the outcome of the mapping activity and able to answer to future experimental needs defined in Work Package1 and 2. Fig. 1. Number of facilities per institutionSEAKNOT-WP3. This paper describes the main outcomes of the critical review performed for MAPEX considering facilities of different stake-holders (universities, research centers, industry, TSOs) in the European Union focused on severe accident research by means of a questionnaire. Valuable information was collected such as type of facilities, their main characteristics in term of operation conditions, severe accident domain, instrumentation, use of data, and appropriateness of data for code validation, operational team, critical issues as funding, retirement of operational/scientific team, future work program, and current funding frameworks. Based on it, a European research platform for experimental investigations can be proposed. 2 Methodology For the purpose of gathering information for the MAPEX, European experimental facilities under operation on severe accident topics and still operational until 2022/2023 were identified within the SEAKNOT-consortium and outside it. Future experimental activity between 2023 and 2030 has been assessed, too. In this approach, attention has been paid to the topics of the experimental programs devoted to single or coupled phenomena that may take place in all phases of a severe accident progression in LWR and SMRs. To achieve these goals, the following methodology has been applied: V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) 3 Fig. 2. List of facilities with the year of commissioning of the SEAKNOT-WP3. –Building of a questionnaire for the experimental mapping activity (see appendix 1) –Identification of test facilities in SEAKNOT-Partners involved in Work Package 3, –Identification of test facilities in SEAKNOT-Partners not involved in Work Package 3, –Identification of test facilities in institutions of EUCountries partners of SEAKNOT but not belonging to the SEAKNOT-consortium, –Identification of test facilities in institutions of EUCountries not partners of SEAKNOT. According to this methodology, the following steps [6] were carried out to draw conclusions about the assessment of the capabilities of the European severe accident experimental facilities: Identify institutions and contact persons to answer the questionnaire. For it, four target groups of institutions were considered: Group1: SEAKNOT-Partners involved in the Work Package 3, Group-2: SEAKNOT-Partners not involved in Work Package 3, Group-3: Institutions in EU-Countries partners of SEAKNOT but not beneficiaries, and Group-4: Institutions in EU-Countries not partners of SEAKNOT. Identify key-persons in all the four-target groups to answer the questionnaire: Evaluate the questionnaire regarding e.g., Total number of test facilities, mapping of experimental facilities with SA research domain, and identify experimental facilities under risky situation regarding funding, research team, and perspective. More details of the methodologies can be found in [6]. Table 1 shows the number of requests sent out and the number of responses/facilities identified by evaluating the questionnaire. One first challenge was concerning the number of answers. As it can be seen in Table 1, SEAKNOT partners have answered but less than one third of organizations outside of SEAKNOT have answered to the questionnaire. Nevertheless, it can be considered that the mapping of European Severe Accident activities is relatively complete because the main severe accident facilities in activity were belonging to SEAKNOT consortium. 3 Quantitative evaluation of the questionnaire The synthesis hereafter is structured around the following topics of relevance for SEAKNOT: main phenomena addressed by research programs of experimental facilities, main severe accident phases covered by programs of experimental facilities, reactor types targeted by experimental programs, experimental programs addressing ATF, experimental programs addressing SMR-issues, experimental facilities without a defined research topic for 4 V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) Table 2. Overview of the severe accidents current and future research programs SEAKNOT-WP3. Institution Name Current SA program-2023 Future SA program (2025–2030) CEA MERARG Nuclear Fuel Industry Research (NFIR) V, VI, VII NFIR VI, ISAC CEA VERDON ISTP, JAEA yes until 2028 CEA CRACOUCASS OECD/ESTER yes until 2028 CEA ATALANTE TCOFF-2, CORIU, TERPF LESSAC under preparation CEA VTI National SA program for LWR Gen II, 3 and 4 (SFR) National SA program, EU SAINET, OECD/NEA COPS CEA ATTILHA Laser heating to investigate high-T behavior of U-containing system OECD/NEA COPS CEA MISTRA Study of SA in PWR focused on H2-risk Sprying in super-heated atmosphere CEA MERELAVA MIT3BAR national project Corium Properties, uncertainties OECD/NEA COPS CEA VULCANO International Cooperation with Japan OECD/NEA COPS CEA KROTOS ICE national program (post-Fukushima), Gen 4 SFR Mitigation OFFERR, SAINET EU CEA SAFeTy Platform not yet Dry/wet MCCI, IVR, Na FCI, open for ATF and SMR, int. Cooperation PANDA QECD/NEA PANDA no PSI HERZSAN International Project. Industry project, national no PSI VEFITA International Project. Industry project, national no PSI TRISTAN National program no PSI ISOLDE no no CIEMAT LASS OFFER, (H-Europe), APIAS (CSN) APIAS (CSN) FRAM JAVA Until 2017 no KIT QUENCH QUENCH-ATF, ATF-TS OECD/NEA projects KIT HYKA None, one in fusion no IRSN TYFON Ongoing PhD Until 2025, then redirection IRSN EPICUR Gamma & LEAR hot cell ESTER OECD Focus on ATF IRSN DOFIN IRSN material qualification no IRSN START until 2024 no IRSN COPIN PhD until 2025 no IRSN MASSE COMPACTE National program no IRSN TOSCAN Study of H2 and aerosol behavior in containment FUK decomtamination (2025), Aerosol mitigation in CONT. naval propulsion IRSN FAAMUS Study of Flash Atomisation Aerosols Mobilization under vacUum System no IRSN PERSEE IRSN internal Polymer ageing project no IRSN IRMA IODINE R&D program of IRSN ODINE R&D program of IRSN KTH CoSMUS ROSAU int. Program National APRI program KTH DEFOR National APRI program APRI: focus on melt fragmentation and debris bed formation KTH MISTEE National APRI program National APRI program KTH MRSPOD National APRI program National APRI program KTH SIMECO-2 National APRI program National APRI program KTH SPaYCOR National APRI program National APRI program UJV BESTH-2 no Project on LWR and SMR UJV THS-15 no Plans for international projects UJV KRNEC Commercial PTS tests program for Czech utility not yet VTT VTT-FP transport NKS-R TRIO Nordic program EURATOM EXCESS IM, SAFER2028 VTT EXSI-PC no NKS nordic program, SAFER2028 VTT VTT-POOL SAFER2028/ALISA project SAFER2028/ALISA project, NUGENIA TA2.4, IPRESCA Project V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) 5 Table 3. Overview of the severe accidents current and future research fields and topicsSEAKNOT-WP3. Institution Name Commisioning SA research fields Topics CEA MERARG 2000 FP source term, fuel relocation LWR, SMR CEA VERDON 2011 Source term, fuel behavior LWR, SMR, ATF CEA CRACOUCASS 2023 Delayed source term LWR CEA ATALANTE 2001 Liquid source term after SA Other: Waste management CEA VITI 2000 In-vessel, Ex-vessel, ST, Containment Gen ll, 3 and 4, ATF, SMR, instrumentation CEA ATTILHA 2016 Chemical systems LWR, SMR, ATF CEA MISTRA 2001 Containment issues e.g., hydrogen risk, steam condensation, turblent gas mixing LWR, SMR, ATF CEA MERELAVA 1397 In-vessel, Ex-vessel, and containment LWR, mitigation, instrumentation CEA VULCANO 1997 Ex-vessel Mitigation, instrumentation CEA KROTOS 2003 FCl, debris bed formation, cooling, mitigation LWR, SMR, ATF, SFR, instrumentation, mitigation CEA SAFeTY Platform 2028 MCCI, FCI, corium properties, IVR LWR, open for SMR and ATF PSI PANDA 1991 Containment, Hydrogen LWR, SMR, mitigation, instrumentation PSI HERZSAN 2022 Source term mitigation Source term mitigation PSI VEFITA 2014 Source term mitigation by FCVS Mitigation of ST for LWRs by wet scrubber FCVS PSI TRISTAN 2008 Pool scrubbing, two-phase flow hydrodynamics Mitigation of ST for LWR’s, pool scrubbing, instrument development PSI ISOLDE 2016 Gas-water two-phase flow mass transfer phenomena Mitigation of ST, pool scrubbing hydrodynamics, instrumentation CIEMAT LASS 1991 Aerosol scrubbing in pools LWR, Mitigatin, instrumentation FRAMATOME JAVA 1989 FP, qualification, performance, mitigation LWR, CANDU, WER KIT QUENCH 1998 In-vessel SA, DBA LWR, ATF KIT HYKA 1999 Containment, hydrogen LWR, SMR, ATF, mitigation IRSN TYFON 2022 Source term, pool scrubbing LWR IRSN EPICUR Gamma & LEAR hot cell 2000 Radiochemistry of FP in SA LWR, ATF, source term IRSN DOFIN 2000 Source term, filterdevices LWR, source term IRSN START 2000 Chemistry-transport LWR, source term IRSN CO PIN 2000 Sump filter dogging LWR IRSN MASSE COMPACTE 2019 In-vessel, ex-vessel LWR IRSN TOSCAN 2000 Containment, Mitigation, decomissioning LWR, H2/aerosol in containment, decommisioning IRSN FAAMUS 2020 ITER fusion Flash atomisation aerosols mobilization under vacuum system, fusion IRSN PERSEE 2017 Radioactive gaseous effluents purification Mitigation IRSN IRMA 1969 Co-60 irradiation, ageing of NPP components Material behavior under irradiation KTH CoSMUS 2022 Ex-vessel LWR KTH DEFOR 2000 FCl including melt fragmentation, debris formation, debris coolability LWR KTH MISTEE 2005 FCl, ex-vessel LWR KTH MRSPOD 2019 In-/Ex-vessel debris bed behavior LWR, in-/ex-vessel KTH SIMECO-2 2021 In-vessel debris behavior, debris bed coolability, dryout, and remelting LWR KTH SPaYCOR 2018 In-vessel retention LWR UJV BESTH-2 2013 IVR, RPV-coolant interactions LWR, SMR UJV THS-15 2018 IVR, CHF VVER-1000 UJV KRNEC 2022 In-vessel, PTS, RPV external cooling LWR, instrumentation VTT VTT-FP transport 2000 In-vessel, source term LWR, SMR, HTGR VTT EXSI-PC 2010 Source term, FP chemistry LWR, SMR VTT VTT-POOL 2018 Source term, containment LWR, SMR, mitigation 6 V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) Table 4. List of institutions and test facilities including the severe accident research field and scaling SEAKNOT-WP3. Institution Name SA research fields Scaling small mid large CEA MERARG FP source term, fuel relocation × CEA VERDON Source term, fuel behavior × CEA CRACOUCASS Delayed source term × CEA ATALANTE Liquid source term after SA × CEA VITI In-vessel, Ex-vessel, ST, Containment × CEA ATTILHA Chemical systems × CEA MISTRA Containment issues e.g., hydrogen risk, steam condensation, turblent gas mixing × CEA MERELAVA In-vessel, Ex-vessel, and containment × CEA VULCANO Ex-vessel × CEA KROTOS FCI, debris bed formation, cooling, mitigation × CEA SAFeTY Platform MCCI, FCI, corium properties, IVR × PSI PANDA Containment, Hydrogen × PSI HERZSAN Source term mitigation × PSI VEFITA Source term mitigation by FCVS × PSI TRISTAN Pool scrubbing, two-phase flow hydrodynamics × PSI ISOLDE Gas-water two-phase flow mass transfer phenomena × CIEMAT LASS Aerosol scrubbing in pools × FRAMATOME JAVA FP, qualification, performance, mitigation × KIT QUENCH In-vessel SA, DBA × KIT HYKA Containment, hydrogen × IRSN TYFON Source term, pool-scrubbing × IRSN EPICUR Gamma & LEAR hot cell Radiochemistry of FP in SA × IRSN DOFIN Source term, filter devices × IRSN START Chemistry-transport × IRSN COPIN Sump filter clogging × IRSN MASSE COMPACTE In-vessel, ex-vessel × IRSN TOSCAN Containment, Mitigation, decomissioning × IRSN FAAMUS ITER fusion × IRSN PERSEE Radioactive gaseous effluents purification × IRSN IRMA Co-60 irradiation, ageing of NPP components × KTH CoSMUS Ex-vessel × KTH DEFOR FCI including melt fragmentation, debris formation, debris coolability × KTH MISTEE FCI, ex-vessel × KTH MRSPOD In-/Ex-vessel debris bed behavior × KTH SIMECO-2 In-vessel debris behavior, debris bed coolability, dryout, and remelting × KTH SPaYCOR In-vessel retention × UJV BESTH-2 IVR, RPV-coolant interactions × UJV THS-15 IVR, CHF × UJV KRNEC In-vessel, PTS, RPV external cooling × VTT VTT-FP transport In-vessel, source term × VTT EXSI-PC Source term, FP chemistry × VTT VTT-POOL Source term, containment × 2024–2030, and experimental programs under critical conditions (man-power shortage, knowledge loss, etc.). 3.1 Experimental facilities operated by SEAKNOT-Partners and their age In Figure 1, the number of severe accident experimental facilities operated by European institutions partners of SEAKNOT is shown. Geographic repartition in Europe is not uniform: more than 50% of these experimental facilities are still operating in 3 main European countries: France (CEA, IRSN), Sweden (KTH) and Switzerland (PSI). The other countries are less involved in experimenFig. 3. List of facilities with the year of commissioning of the SEAKNOT-WP3. V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) 7 Fig. 4. List of facilities with the year of commissioning of the SEAKNOT-partners not involved in SEAKNOT WP3. tal activities whereas a lack of experimental data has been identified by the SEAKNOT partners [4]. The time life of experimental facilities is also an important parameter. In the frame of SEAKNOT assessment activity of severe accident facilities still in operation, it has been asked to SEAKNOT partners to provide insights into the average age of the experimental facilities (Fig. 2). Furthermore, an overview of the facilities expected to remain operational until 2030 for future R&D activities has been also assessed. European severe accident facilities are relatively old: the majority of the test facilities were constructed between the eighties and end of the nineties, meaning that their average age is around 30 years. The maintenance of old facilities are crucial but very expensive, meaning possible closure by 2030. 3.1.1 Severe accident current and future research programs Based on the information collected, an important aspect was to identify in which current and future research programs the facilities are involved or not. This information is essential for assessing the capability of European experimental facilities to meet both current and future (2030) research needs, derived from SEAKNOT PIRT activities (WP1) and to propose future European programs in order to answer to nuclear safety challenge for SMRs and new mitigation tool for nuclear energy in Europe. Table 2 lists the facilities with the current and future severe accident programs in which the facilities are involved. The majority of European severe experimental facilities have some domestic and international programs, but almost no European program activities. But, some experimental facilities at IRSN (France), PSI (Switzerland) and KIT (Germany) have no program planned for the period 2025–2030, meaning in most unfavorable situation the mothballing of the facilities, leaving them vacant while continuing to cover maintenance costs. European experimental expertise in the field of severe accident has taken several years and has been very costly for European community whereas it can be lost rapidly if any European program in the 2025–2030 is proposed. 3.1.2 Severe accident fields and topics addressed by the experimental facilities Based on the information collected, an important aspect was to identify the actual research topics of test facilities. This information will be useful for identifying relevant topics for which only a limited number of experimental facilities are available. In Table 3, the experimental facilities are listed with their respective severe accident research fields and topics provided in the questionnaire. Almost all severe accident topics, identified in the frame of SEAKNOT project, are covered as it can be seen in Table 3. But it will be only at the end of the PIRT activity of SEAKNOT that it will be possible to assess if European facilities can answer to all experimental needs in the field of severe accident for the period 2025–2030. Experiment facilities are focused on quite diverse research fields and mainly related to LWRs including CANDU reactors and water-cooled SMRs. It is impor- 8 V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) Table 5. Overview of the severe accident research fields and topics addressed by the facilities of the SEAKNOTpartners not involved in WP3. Institution Facility name Start Short description Severe accident Topics operation Research fields BT THAU/THAI+ 2000 Study of behaviour of hydrogen, iodine and aerosols in the containment of light water reactors during severe accidents TH, H2, PAR, FP, Pool scrubbing LWR, SMR, Mitigation, Instrumentation, passive systems BT BATL 2015 Study of aerosol behaviour in light water reactors durinq severe accidents FP, Aerosols, FCVS, passive systems FZJ REKO Platform 1997 Study of PARS behavior Containment, Severe Accidents, Hydrogen Mitigation LWR, SMR, Mitigation FZJ SAAB/IN EX 2014 Study of pool scrubbing phenomena and particle depletion/interaction Containment, Aerosol Behaviour, Pool Scrubbinq LWR, SMR FZJ SETCOM 2014 Separate Effect Tests on Condensation Modeling Containment TH LWR, instrumentation, SMR Table 6. Overview of the current and future research programs of the different facilities run by the SEAKNOT-partners not involved in WP3. Institution Facility name Start Short descrption Current severe accident Future severe accident operation program 2023 program 2024–2030 BT THAU/THAI+ 2000 Study of behaviour of hydrogen, Iodine and aerosols in the containment of light water reactors during severe accidents THEMIS, THAI PVII, IPRESCA THEMIS, nat. THAI BT BATL 2015 Study of aerosol behaviour in light water reactors durinq severe accidents Coop, with FRAM FZJ REKO Platform 1997 Study of PARS behavior EU AMHYCO, nat. NUSAFE EU SASPAM, NUSAFE SMR FZJ SAAB/INEX 2014 Study of pool scrubbing phenomena and particle depletion/interaction NUSAFE POF IV EU SASPAM, NUSAFE SMR FZJ SETCOM 2014 Separate Effect Tests on Condensation Modeling BMWi KEK, SETCOM CFD-development, contaiment tant to note that no specific tests for SMR are devoted to severe accident conditions, except the ones dedicated to passive heat removal systems. The tests devoted to mitigation are related to source term and containment issues. 3.1.3 Experimental facilities and scaling Table 4 lists the different facilities along with their operator, facility name, associated severe accident research fields, and the scaling information. For severe accident studies and nuclear safety, scaling effect is crucial to be able to have reliable data for extrapolation to reactor case. The majority of the test facilities are devoted to PWRs, and BWRs, some to VVER, and CANDU (current generation 2 European fleet). SMRs activity is also concerned, but no specific facility is strictly devoted to severe accident studies for SMRs. The majority of the facilities are categorized as of medium and largescale. Only few of them are of small scale mainly to perform analytical studies. Based on this classification, 21 facilities are categorized as “large-scale”, 18 as “mid-scale” and 3 as small-scale facilities. However, this declared categorization by the facility technical staff, should be technically supported in case of future application for SMR SA investigation, whatever the design. 3.2 Experimental facilities operated by SEAKNOT-Partners not involved in WP3 The SEAKNOT-partners not involved in the WP3have also answered to the SEAKNOT questionnaire (Fig. 3). Five facilities are operated by two German institutions, namely Becker Technologies (BT) and Research Center J¨ulich (FZJ). Figure 4 shows the starting dates of the operation of the facilities operated by two German institutions. These facilities are recently operated (after 2000) except for REKO. Table 5 summarizes the current research fields and topics addressed by the five facilities. The main topics of severe accident research are devoted to containment phenomena during severe accidents relevant for LWRs and SMRs. Some activities are planned till 2030 mainly focused on CFD approach and SMRs application (Tab. 6). V.H. Sanchez-Espinoza et al.: EPJ Nuclear Sci. Technol. 11, 75 (2025) 9 4 Summary and conclusions In the frame of the European project SEAKNOT (Severe Accident research and KNOwledge management) project, an analysis and mapping of European severe accident research facilities currently under operation has been performed. Through a general questionnaire, SEAKNOT partners have been able to answer about their current and future (2025–2030) experimental activities in the field of severe accidents including LWRs and SMRs. The questionnaires evaluated comprise data of 59 facilities. A systematic evaluation of the provided information was performed, which included the description of the facilities, current and future research focus, main severe accident phenomena addressed, reactor types considered. In this context, particular attention was given to identify research programs addressing new topics such as ATF and SMRs. The information collected and the evaluation performed pave the way for the mapping of European severe accident facilities under operation and it allows to identify experimental needs in the severe accident research for LWRs and SMRs until 2030. In 2025, the main topics interesting severe accident studies LWRs and SMRs are covered by several experimental facilities belonging to SEAKNOT consortium. 22 experimental facilities do not have concrete “research plan” established yet for the period 2024–2030 which is a bad indicator for research in nuclear safety. European experimental expertise in the field of severe accident has taken several years and has been very costly for European community. This level of excellence, recognized worldwide, can be lost rapidly if any European program in the 2025–2030 takes into account the field of severe accident for the current and future nuclear fleet. Acknowledgments The authors would like to acknowledge the work and thank all the participants of SEKNOT project funded by the European Union under the grant Agreement No. 101060327. Views and opinions expressed are those of the Authors only and do not necessarily reflect those of the European Union or EUROATOM. Neither the European Union nor the granting authority can be held responsible for them. Funding The authors thank the Horizon 2020 SEAKNOT project SEKNOT project funded by the European Union under the grant Agreement No. 101060327. Conflicts of interest Authors VHSE, PP, and LEH certify that they have no financial conflicts of interest (e.g., consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) in connection with this article. Data availability statement Data associated with this article cannot be disclosed due to legal reason of the different owner of the data. Author contribution statement VHSE: Writing, Editing, Conceptualization, Formal Analysis, Methodology, Data Curation, Investigation, PP: Reviewing, Conceptualization, Investigation, Reviewing, LEH: Funding acquisition, Reviewing, Methodology. References 1. NEA, NEA Small Modular Reactor Dashboard, NEA No. 7671, OECD, Paris, 2024 2. IAEA, Network for Experiment and Code Validation Sharing (NEXSHARE), IAEA, 22/02/2024, https://nucleus.iaea.org/sites/connect/NEXPublic/ SitePages/Home.aspx, [Accessed 18/03/2025] 3. SNETP, OFFERR-European User Facility Network, SNETP, 01/2023, https://snetp.eu/offerr/, [Accessed 18/03/2025] 4. L.H. Herranz, SEAKNOT – Severe Accident Research and Knowledge Management for LWRs (SEAKNOT, Madrid, 2023) 5. L.E. Herranz, S. Gupta, S. Paci, P. Piluso, SEAKNOT: Looking ahead of severe accident research, Ann. Nucl. Energy 218, 111390 (2025) 6. V.H. Sanchez-Espinoza, P. Piluso, Mapping of European Severe Accident Facilities (D3.1) (SEAKNOT, Karlsruhe, 2023) Cite this article as: Victor Hugo Sanchez-Espinoza, Pascal Piluso, Luis Enrique Herranz. Identification of European experimental facilities for severe accident research within EU SEAKNOT-project: Analysis and mapping, EPJ Nuclear Sci. Technol. 11, 75 (2025). https://doi.org/10.1051/epjn/2025071