Education, training and mobility: towards a common effort to assure a future workforce in Europe and abroad

The paper highlights the main features of some Euratom projects, which have been running recently in support to education, training and mobility in the nuclear fields. The described projects address various critical aspects of nuclear knowledge management, aiming at maintaining the wealth of nuclear expertise in Europe in an environment characterised by decreased attractiveness of nuclear careers. In an effort to broaden the cooperation and to further extend the opportunities for mobility, some projects ran in parallel with similar initiatives undertaken beyond the European borders. The lesson learnt in terms of successes achieved and critical aspects revealed by the different actions are finally discussed also considering recent recommendations and assessed scenarios by the European Commission for the decarbonisation of the energy sector

International Conference Nuclear Energy in Central Europe 2001 VALIDATION OF RALOC4 CODE FOR IGNALINA NPP ACCIDENT LOCALISATION SYSTEM EMPLOYING PARAMETERS MEASURED DURING MSV OPENING

ABSTRACT Accident Localisation System (ALS) of Ignalina NPP is a pressure suppression type confinement. It consists of a number of interconnected compartments with 10 condensing pools to condense the accident-generated steam and to reduce the peak pressures that can be reached during any LOCA. The condensing pools are located at five elevations in two ALS towers. In the case of main safety valve (MSV) opening the released steam is directed to the top (5 th ) condensing pool of ALS. The ALS thermal hydraulic parameters measured during unintended opening of single MSV which appeared on November 8, 1998 at Ignalina NPP Unit 2 were used for validation of RALOC4 code (Germany). Post-event calculations performed and the calculated water temperatures and water levels in condensing pools as well as condenser tray cooling system (CTCS) parameters were compared with corresponding measured data. The results of the performed sensitivity analysis showed that in the best-estimate analysis the heat transfer coefficient in CTCS heat exchangers could be increased to 2500 W/(m 2 ⋅K) compared to conservative value of 1000 W/(m 2 ⋅K) applied in former calculations

TSO Perspectives to Review a Reactor Concept based on In-Vessel melt Retention (IVR) Strategy for Severe Accident Management

International audienceIn-Vessel melt Retention (IVR) is a Severe Accident (SA) mitigation measure applied in some Pressurized Water Reactors (PWRs) in order to cool down molten fuel (corium) inside the Reactor Pressure Vessel (RPV) by flooding the reactor cavity and cooling the RPV external surface with water. The safety demonstration provided to a national safety authority to support a reactor concept crediting the IVR strategy to enhance safety of an existing plant or to license a new generation design can be based on both deterministic and Probabilistic Risk Assessment (PRA). Experimental data can be used to support analyses or to validate models implemented in computer codes. This paper provides Technical Safety Organisations (TSOs) perspectives to review IVR as SA mitigation measure applied in NPP. The paper is structured as it is advised in the European Technical Safety Organisations Network (ETSON) Technical Safety Assessment Guide ETSON/2013-003

Safety assessment for EU DEMO – Achievements and open issues in view of a generic site safety report

The way to arrive at a licensing phase for a nuclear fusion installation is not straightforward mainly because of the lack of operating experience and of dedicated nuclear regulations. In fact, only small/medium experimental facilities exist with limited licensing processes and only one large experiment, ITER, has obtained a construction license. Therefore, the safety assessment and the preparation of the preliminary safety report is almost a first of a kind for DEMO. Taking advantage of the fission power plants experience and considering to the maximum extent the ITER safety studies, the preparation of a Generic Site Safety Report (GSSR) has begun. It will require some years to be completed; however currently, at the starting point, the strategy to develop it is clear and well defined. This paper considers all the safety issues that will be included in the GSSR because they have been clarified in the frame of the European Work programme for DEMO from 2014 up to 2018, and should not be modified in the future, such as the safety requirements for the plant and the systems, the tools to be used for the safety assessment, the procedures for the selection of the reference accidents, and so on. Together with these topics, considered as goals achieved, there are others for which an additional effort is necessary because they do not cover all the expected requirements of the likely licensing procedures applicable for DEMO. A complete spectrum of Design Basis Accidents and Beyond Design Basis Accidents that can determine the risk of releases from the main systems of the power plant is still incomplete together with the safety classification of most of the Structures, Systems and Components, and the feasibility and analyses of some accident mitigation systems. The outcome of this study is the quantification, when possible, of the gap between the results achieved and the goals established in the power plant guidelines. It will help also to qualify the effort required in terms of studies, experiments and human resources to reach a good stage for successful DEMO licensing

Sprays in Containment: Final results of the SARNET Spray Benchmark

The influence of containment sprays on atmosphere behaviour, a sub-task of the Work Package WP12-2 CAM (Containment Atmosphere Mixing), has been investigated through benchmark exercises based on TOSQAN (IRSN) and MISTRA (CEA) experiments. These tests are being simulated with lumped-parameter (LP) and Computational Fluid Dynamics (CFD) codes. Both atmosphere depressurization and mixing are being studied in two phases: a ‘thermalhydraulic part’, which deals with depressurization by sprays (TOSQAN 101 and MISTRA MASPn), and a ‘dynamic part’, dealing with light gas stratification break-up by spray (TOSQAN 113 and MISTRA MARC2b). In the thermalhydraulic part of the benchmark, participants have found the appropriate modelling to obtain good global results in terms of experimental pressure and mean gas temperature, for both TOSQAN and MISTRA tests. It can thus be considered that code users have a good knowledge of their spray modelling parameters. On a local level, for the TOSQAN test, single droplet behaviour is found to be well estimated by some calculations, but the global modelling of multiple droplets, i.e. of the spray, specifically for the spray dilution, is questionable in some CFD calculations. It can lead to some discrepancies localized in the spray region and can thus have a high impact on the global results, since most of the heat and mass transfers occur inside this region. In the MISTRA tests, wall condensation mass flow rates and local temperatures were used for code-experiment comparison and show that improvement of the local modelling, including initial conditions determination, is needed. In this dynamic part, a general result, in both tests, is that calculations do not recover the same kinetics of the mixing. Furthermore, concerning global mixing, LP contributions seem not suitable here. For the TOSQAN benchmark, the one-phase CFD calculations recover partially the phenomena involved during the mixing, whereas the two-phase flow CFD contributions generally recover the phenomena. Moreover, one important result is also that none of the contributions finds the exact amount of helium remaining in the dome above the spray nozzle in the TOSQAN 113. Discrepancies are rather high (above 5%vol of helium). Results are thus encouraging, but the level of validation should be improved. The same kind of conclusions can be drawn for the MISTRA MARC2B tests. As a conclusion of this SARNET spray benchmark, the level of validation obtained here is encouraging for the use of spray modelling for risk analysis. However, some more detailed investigations are needed to improve model parameters and decrease the uncertainty for containment applications as well as to increase the predictability of the phenomena within the containment analyses. Further activities are well encouraged on this topic, such as numerical benchmarks on analytical separate-effect experiments