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This report is a result of a detailed and comprehensive review of available experimental database focusing on fuel rod failures, on fission product releases from fuel rods and on activity transport up to the environment during LOCA and SGTR events. It also includes available information issued from the monitoring of normal operation and transients in NPPs and from some accidental scenarios. The review covers all important LOCA and SGTR phenomena in PWRs and VVERs by experimental data and is expected to support the code and model validation activities within the R2CA H2020 project. More than 40 test series is included in the report. For each test series a description is provided where the test objectives, the tested materials, the experimental facility, the measured parameters and Post Irradiation Examination data are provided together with the general conclusions drawn after the test completion. In addition, three large matrices have been compiled to support detailed discussions on 1/ Phenomena 2/ Test characterization 3/ data availability. These matrices are displayed in the attachment of this report. The common use of data from small scale separate effect test and integral tests provides possibilities for the improved simulation of several phenomena (e.g. cladding burst, oxidation, hydrogen uptake, activity release and transport) under very different conditions. Most of these conditions can be considered typical for LOCA and SGTR events,while some of them cover wider parameter ranges than those which currently take place in these accidents.

This report covers the current capabilities of the available codes that will be used within the R2CA H2020 project in the release evaluation methodologiesof LOCA and SGTR transients in different kinds of reactors (PWRs, VVERs, EPR, BWR) displayingboth code descriptions and model comparison tables. It includes both system codes and codes focusing on a part of the phenomenology only, in particular focusing on the determination of the fuel rod failures as well as on the consequences of these failures. A state of the art of the combined use of these codes in implementation of the release evaluation methodologies is also described. The work that has been done covers fuel performance, sub-channel and system thermal-hydraulics, radionuclide transport and integral system behaviour. Codes modelling only the steady-state operation (especially fuel codes) have also been included as they produce initial conditions for the transient codes and are integral part of the calculation chains. Finally, the developments items for the codes, that will be addressed within the R2CA project, are also summarized dealing with cladding modelling, fuel and fission product modelling, code coupling and whole core modelling and nodalization.&nbsp

The paper deals with the evaluation of the Fukushima-Daiichi Nuclear Power Plant (NPP) accident in Units 1 to 4: an attempt is made to discuss the scenario within a technological framework, considering precursory documented regulations and predictable system performance. An outline is given at first of the NPP layout and of the sequence of major events. Then, plausible time evolutions of relevant quantities in the different Units, is inferred based on results from the application of numerical codes. Scenarios happening in the primary circuit and containment (three Units involved) are distinguished from scenarios in spent fuel pool (four Units involved). Radiological releases to the environment and doses are approximately estimated. The event is originated by a natural catastrophe with almost simultaneous occurrence of earthquake and tsunami. These caused heavy destruction in a region in Japan much wider than the land around the NPP which was affected by the nuclear contamination. Key outcome from the work is the demonstration of strength for nuclear technology; looking at the past, misleading Probabilistic Safety Assessment (PSA) data and inadequacy in licensing processes have been found. Looking into the future keywords are Emergency Rescue Team (ERT), Enhanced Human Performance (EHP), and Robotics in Nuclear Safety and Security (RNSS).