The European Journal of Physics N (EPJ-N)
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Innovative and safe supply of fuels for reactors
No full textWithin the Euratom research and training program 2014–2018, three projects aiming at securing the fuel supply for European power and research reactors have been funded. Those three projects address the potential weaknesses – supplier diversity, provision of enriched fissile material – associated with the furbishing of nuclear fuels. First, the ESSANUF project, now terminated, resulted in the design and licensing of a fuel element for VVER-440 nuclear power plant manufactured by Westinghouse. The HERACLES-CP project aimed at preparing the conversion of high performance research reactor to low enriched uranium fuels by exploring fuels based on uranium-molybdenium. Finally, the LEU-FOREvER pursues the work initiated in HERACLES-CP, completing it by an exploration of the high-density silicide fuels, and including the diversification of fuel supplier for soviet designed European medium power research reactor. This paper describes the projects goals, structure and their achievements
Effects of the initial granular structure of clay sealing materials on their swelling properties: experiments and DEM simulations
No full textPellet-based expansive clay materials are considered as a sealing material for closing the galleries in radioactive waste disposal concepts. In repository conditions, the granular mixture progressively homogenises upon hydration by the host rock pore water. The present study focuses on the material behaviour before homogenisation. A grain-scale experimental characterisation is first performed in the laboratory. A model describing the hydromechanical behaviour of a pellet is proposed based on the experimental results. Then, suction-controlled swelling pressure tests are performed in the laboratory. Using Discrete Element Method (DEM) and the model proposed for a single pellet, the tests are successfully simulated. It is highlighted that (i) the swelling pressure evolves in two phases in the investigated suction range, controlled by the granular structure of the mixture; (ii) wall effects at the laboratory scale affects the material response; (iii) measurement variability associated to the sensor diameter is non-negligible; (iv) DEM is a valuable tool able to provide insight into the material behaviour
Empirical estimation of uncertainties of Charpy impact testing transition temperatures for an RPV steel
No full textThe aim of the present work is to derive empirically a simple expression of the uncertainties on Charpy transition temperatures (TT), which depends only on the test temperatures and the number of tests at each of these temperatures. Calculations of the TT uncertainties of a RPV steel are performed based on an empirical representation of Charpy test results and a Monte Carlo procedure to generate large numbers of data sets for different test matrices. Applying usual procedures to determine the TT to the generated data sets gives access to the distributions of these quantities from which the uncertainties are calculated.An analytical expression for these uncertainties is proposed
A minimal predictive model for better formulations of solvent phases with low viscosity
No full textThe viscosity increase of the organic phase when liquid–liquid extraction processes are intensified causes difficulties for hydrometallurgical processes on industrial scale. In this work, we have analyzed this problem for the example of N,N-dialkylamides in the presence of uranyl nitrate experimentally. Furthermore, we present a minimal model at nanoscale that allows rationalizing the experimental phenomena by connecting the molecular, mesoscopic and macroscopic scale and that allows predicting qualitative trends in viscosity. This model opens broad possibilities in optimizing constraints and is a further step towards knowledge-based formulation of extracting microemulsions formed by microstructures with low connectivity, even at high load with heavy metals
INSIDER UC2: the BR3 biological shield preliminary results and future work
No full textAiming at economical optimization, the characterisation of the biological shield of the Belgian Reactor 3 is one of the three use cases intended to validate the integrated characterization methodology developed within the INSIDER project. Pre-existing data were used to define the sampling design strategy. The additional sampling and analysis program consisted of total gamma measurements at the inner surface of the biological shield (secondary data) and gamma spectrometry measurements on drill core samples (primary data). The newly acquired data is supplemented with the historical available data. The full data set currently consists of a total of 283 secondary and 379 primary data points. Preliminary calculations already provide a clear-cut representation of the three different end-stage classes: unconditional clearance, conditional clearance and radioactive waste. On the short term, the current model will be further refined and completed with proper risk evaluation. On the longer term, we envisage a global uncertainty calculation and sensitivity analysis of the entire process
Innovative Gen-II/III and research reactors' fuels and materials
No full textThis manuscript presents important material challenges regarding innovative Gen-II/III nuclear systems and research reactors. The challenges are discussed alongside the key achievements so far realised within the framework of 4 EU-funded projects: H2020 IL TROVATORE, FP7 MULTIMETAL, FP7 MATTER and FP7 SCWR-FQT. All the four Projects deal with innovative researches on materials to enhance the safety of nuclear reactors. IL TROVATORE proposes new materials for fuel cladding of PWR reactors and tests in order to really find out an “Accident Tolerant Fuel” (ATF). MULTIMETAL focused on optimization of dissimilar welds fabrication having considered the field performances and dedicated experiments. MATTER carried on methodological and experimental studies on the use of grade 91 steel in the harsh environment of liquid metal cooled EU fast reactors. SCWR-FQT focused on fuel qualification of Supercritical Water Reactor including the selection of the better material to resist the associated high thermal flux
Influence of the dissolved hydrogen concentration on the radioactive contamination of the primary loops of DOEL-4 PWR using the OSCAR code
No full textCorrosion products are generated in the primary circuit during normal operation and are activated in the core. Those activated corrosion products, mainly 58Co and 60Co (coming respectively from the activation of 58Ni and 59Co), are then transported by the primary fluid and deposited on the out-of-flux surfaces (steam generators, primary coolant pipes…). To minimize this radioactive contamination, one needs to understand the behavior of corrosion products by carrying out measurements in PWRs and test loops combined with a reactor contamination assessment code named OSCAR. The aim of this article is to evaluate the influence of the change in the Dissolved Hydrogen (DH) concentration on the contamination of the primary loops of DOEL-4 PWR, a Belgian unit. After the description of the principle of the OSCAR V1.3 code, its use is illustrated with the simulation of DOEL-4. Finally, those calculations are compared to autoclave experiments called DUPLEX with thermodynamic and chemical conditions closed to those observed in PWRs. OSCAR V1.3 calculations show that an increase in the DH concentration results in a decrease in 58Co surface activities. These results are consistent with those from the DUPLEX experiments. Finally, an increase of the DH concentration is then recommended in operating PWRs to reduce the 58Co surface contamination
Infrastructure and international cooperation in research and knowledge transfer: supporting access to key infrastructures and pan-European research − lessons learned
No full textAccess to research infrastructures has been supported by the European Commission under different financial schemes. During the 6th EURATOM Framework Programme the instrument introduced by the European Commission were the Integrated Infrastructure Initiatives (I-3). Moreover, funding schemes to support Education and Training for students and professional developments were defined also. The main difference between these two funding schemes is that I-3 are topic-driven projects with access to infrastructure components, while the Education and Training related projects have a mobility component that is applied for the different research topics. The outcome of projects as TALISMAN (I-3), EFNUDAT/NUDAME (I-3), GENTLE (mobility), ENEN-plus (mobility), NUGENIA-plus (mobility within TA of NUGENIA) and ESNII-plus (I-3 similar) will be shortly presented as well as the future European Commission plans in the field of access to research infrastructure
Fuel fabrication and reprocessing issues: the ASGARD project
No full textThe ASGARD project (2012–2016) was designed to tackle the challenge the multi-dimensional questions dealing with the recyclability of novel nuclear fuels. These dimensions are: the scientific achievements, investigating how to increase the industrial applicability of the fabrication of these novel fuels, the bridging of the often separate physics and chemical communities in connection with nuclear fuel cycles and finally to create an ambitious education and training platform. This will be offered to younger scientists and will include a broadening of their experience by international exchange with relevant facilities. At the end of the project 27 papers in peer reviewed journals were published and it is expected that the real number will be the double. The training and integration success was evidenced by the fruitful implementation of the Travel Fund as well as the unique schools, e.g. practical and theoretical handling of plutonium
Hydraulic and statistical study of metastable phenomena in PWR rod bundles
No full textThe analysis of fuel rod bundle flows constitutes a key element of Pressurized-Water Reactors (PWR) safety studies. The present work aims at improving our understanding of nefarious reorganisation phenomena observed by numerous studies in the flow large-scale structures. 3D simulations allowed identifying two distinct reorganisations consisting in a sign change for either a transverse velocity in rod-to-rod gaps or for a subchannel vortex. A Taylor “frozen turbulence” hypothesis was adopted to model the evolution of large-scale 3D structures as transported-2D. A statistical method was applied to the 2D field to determine its thermodynamically stable states through an optimization problem. Similarities were obtained between the PWR coherent structures and the stable states in a simplified 2D geometry. Further, 2D simulations allowed identifying two possible flow bifurcations, each related to one of the reorganisations observed in 3D simulations, laying the foundations for a physical explanation of this phenomenon