Neutronic study of slightly modified water reactors and application to transition scenarios

International audienceIn this paper we have studied slightly modified water reactors and their applications to transition scenarios. The PWR and CANDU reactors have been considered. New fuels based on Thorium have been tested : Thorium/Plutonium and Thorium/Uranium- 233, with different fissile isotope contents. Changes in the geometry of the assemblies were also explored to modify the moderation ratio, and consequently the neutron flux spectrum. A core equivalent assembly methodology was introduced as an exploratory approach and to reduce the computation time. Several basic safety analyses were also performed. We have finally developed a new scenario code, named OSCAR (Optimized Scenario Code for Advanced Reactors), to study the efficiency of these modified reactors in transition to GenIV reactors or in symbiotic fleet

Natura Alert: Monitoring biodiversity threats using citizen science

Since the late 1970s, the BirdLife Partnership has been working collectively to identify, document and protect places on the Earth with the greatest significance for the conservation of the world’s birds. As a result, over 13,000 Important Bird and Biodiversity Areas (IBAs) have been identified. However, we lack comprehensive monitoring of the condition of these sites, with an increasing number of IBAs under threat from damaging development – the majority of which appears to be poorly planned and does not take environmental values into account. Sites face a wide range of problems, which require an equally wide range of solutions. To address this problem, Natura Alert has been developed within the Horizon 2020-funded LandSense Citizen Observatory project. Natura Alert is a mobile app and web portal that allows users to pinpoint the location of threats to biodiversity and habitat changes, to prevent the further damage or loss to our biodiversity. We are particularly interested in threats that are occurring inside IBAs, Key Biodiversity Areas (KBAs) and Natura 2000 sites in the European Union, although submitting records in other areas is also possible. Information on the condition of these sites, the threats to them, the conservation measures in place and the changes in these aspects over time are essential to set priorities, hold governments to account and inform policies and decision-makers. Volunteers can share their observations with the wider community and help to map the state of our most valuable sites around the world. They can download our mobile app to quickly record their observations in the field or use the web app to discover more functionalities, such as visualizing reports from other users, creating dashboards per country and downloading their own reports. Natura Alert is being tested in Spain and Indonesia, thanks to the volunteer network of two BirdLife partners: SEO/BirdLife and Burung. While the Spanish volunteers are focusing on threats to birds and habitats within IBAs and Natura 2000 sites, the Indonesian communities are validating alerts from satellite-image analysis for forest change on Flores island. Citizen observations trigger real-time alerts to national and regional IBA/KBA coordinators at BirdLife International, who will ensure that the data are of high quality and produce regional and global monitoring assessments that could help monitor the indicators of the Sustainable Development Goals (SDGs) and the Convention on Biological Diversity (CBD). Also, researchers and practitioners around the globe can benefit from this type of data, as well as institutions and stakeholders from the private sector willing to make better decisions based on high quality data via the Integrated Biodiversity Assessment Tool (IBAT)

Natura Alert: Monitoring biodiversity threats using citizen science

Since the late 1970s, the BirdLife Partnership has been working collectively to identify, document and protect places on the Earth with the greatest significance for the conservation of the world’s birds. As a result, over 13,000 Important Bird and Biodiversity Areas (IBAs) have been identified. However, we lack comprehensive monitoring of the condition of these sites, with an increasing number of IBAs under threat from damaging development – the majority of which appears to be poorly planned and does not take environmental values into account. Sites face a wide range of problems, which require an equally wide range of solutions. To address this problem, Natura Alert has been developed within the Horizon 2020-funded LandSense Citizen Observatory project. Natura Alert is a mobile app and web portal that allows users to pinpoint the location of threats to biodiversity and habitat changes, to prevent the further damage or loss to our biodiversity. We are particularly interested in threats that are occurring inside IBAs, Key Biodiversity Areas (KBAs) and Natura 2000 sites in the European Union, although submitting records in other areas is also possible. Information on the condition of these sites, the threats to them, the conservation measures in place and the changes in these aspects over time are essential to set priorities, hold governments to account and inform policies and decision-makers. Volunteers can share their observations with the wider community and help to map the state of our most valuable sites around the world. They can download our mobile app to quickly record their observations in the field or use the web app to discover more functionalities, such as visualizing reports from other users, creating dashboards per country and downloading their own reports. Natura Alert is being tested in Spain and Indonesia, thanks to the volunteer network of two BirdLife partners: SEO/BirdLife and Burung. While the Spanish volunteers are focusing on threats to birds and habitats within IBAs and Natura 2000 sites, the Indonesian communities are validating alerts from satellite-image analysis for forest change on Flores island. Citizen observations trigger real-time alerts to national and regional IBA/KBA coordinators at BirdLife International, who will ensure that the data are of high quality and produce regional and global monitoring assessments that could help monitor the indicators of the Sustainable Development Goals (SDGs) and the Convention on Biological Diversity (CBD). Also, researchers and practitioners around the globe can benefit from this type of data, as well as institutions and stakeholders from the private sector willing to make better decisions based on high quality data via the Integrated Biodiversity Assessment Tool (IBAT)

Neutron-induced fission cross sections of short-lived actinides with the surrogate reaction method

Neutron-induced fission cross sections for 242,243Cm and 241Am have been obtained with the surrogate reaction method. Recent results for the neutron-induced cross section of 243Cm are questioned by the present data. For the first time, the 242Cm cross section has been determined up to the onset of second-chance fission. The good agreement at the lowest excitation energies between the present results and the existing neutron-induced data indicates that the distributions in spin and parity of states populated with both techniques are similar

Preliminary design studies by a complete academic simulation toolbox of a water-cooled thorium-fueled small modular reactor core

International audienceA simple methodology has been developed for the design of competitive PWR-likereactors. It is illustrated by a Small Modular Reactor (SMR) loaded with thorium fuel andtargeting an ambitious final burnup. The complexity of the tested nuclear cores is managed byprogressively increasing the level of simulation detail and taking into account the relatedoperating constraints. For sufficient design margin, various moderation ratio values have beenconsidered. By means of our C++ framework SMURE (Serpent/MCNP Utility for ReactorEvolution), fuel evolution is first computed at the mirrored assembly scale, then at the full corescale with power flattening. Particular care is taken to make reactivity management, by standardsoluble boron completed by an optimized suite of burnable poisons, realistic at both scales. Safetyrequirements are finally tested on a typical Rod Ejection Accident (REA). This core transientcalculation relies on our diffusion-based Nodal Drift Method (NDM) coupled to our 1D-RZtime-dependent code BATH (Basic Approach to Thermal-Hydraulics)

Enhancements to the Nodal Drift Method for a Rod Ejection Accident in a PWR-like mini-core with lumped thermal model

International audiencePrevious burnup calculations of High Conversion Water Reactor (HCWR) options have given promising fuel cycle results. Now safety must be assessed. This requires the development of academic computing tools, coupling as simply as possible neutronics and thermal-hydraulics. The diffusion-based Nodal Drift Method (NDM) for spatial core analysis has been developed towards a broad and coarse safety review of the most promising candidates. NDM has been already validated on a simplified CANDU LOCA benchmark, without thermal coupling. Dedicated to the calculation of a Rod Ejection Accident (REA) as defined by a recent PWR-like mini-core benchmark, the present work describes and validates all the necessary enhancements to NDM. A first 2D geometry with coupling to a lumped thermal model has been validated. Then, 3D features including a refined model for the ejected control rod have been added. Particular attention has been paid on the analysis of discrepancies with reference results. Limitations due to the oversimplified lumped thermal model are finally discussed

Development and dual validation on a transient inspired by KRUSTY of the sNDM diffusion method for easy, MC-based, core analysis

International audienceSuccessfully validated on a typical CANDU LOCA and fruitfully applied to safety assessment studies of high conversion water-cooled cores, the Nodal Drift Method (NDM) has recently been generalized. The so-called “super NDM” (sNDM) methodological product offers an even simpler way to core analysis, basically by feeding the diffusion approximation with specific adjustments from Monte Carlo calculations. The test case chosen for validation has been inspired by the KRUSTY experiment of a fast small UMo core driven by its radial BeO reflector, and is defined by a MCNP model of a few cells. The selected heat-up transient consists in a slow reactivity insertion, from nominal steady-state, of 120 pcm in 600 s. Fuel power and average temperature increase from about 2200 W and 1000 K up to 2500 W and 1100 K at the new equilibrium reached one hour later. Using an axisymmetric structured mesh, large nodal volumes and appropriate MCNP tallies, sNDM manages to reproduce the exact same initial equilibrium as its Monte Carlo reference. Lightly completed for reactivity insertion and thermal feedback, sNDM is doubly validated by comparison to both known-valid point kinetics over the whole transient and MCNP neutron balance for two remarkable states. Such a simplifying and promising approach, making full use of MC-based diffusion, is methodologically discussed. Further development effort and small core design applications are finally proposed

Validation of the Nodal Drift Method on a CANDU LOCA and First Application to the TWIGL Seed-Blanket REA

International audienceThe Nodal Drift Method (NDM) has been developed for a broad and coarse safety review ofpromising thorium-fueled High Conversion Water Reactor (HCWR) options. Conceived as a missing linkbetween too approximate point kinetics and too sophisticated industrial codes, NDM is based on 2-groupdiffusion theory and a lumped parameter model with maximized mesh size. It has been validated on aCANDU LOCA (Loss Of Coolant Accident) benchmark, without any need for thermal calculations. Withsame principle of pre-tabulated cross sections and as a first application to PWR-like REA (Rod EjectionAccident), the well-known TWIGL benchmark of a ramp transient within a heterogeneous core has beencalculated. From its good results have been deduced a few perspectives towards future HCWR studies

Validation of the minimalistic Nodal Drift Method for spatial kinetics on a simple CANDU LOCA benchmark

International audienceThe recently developed Nodal Drift Method (NDM) provides easy spatial kinetics with a view to broad and coarse safety studies of some promising thorium-fueled High Conversion Water Reactor (HCWR) options. It fills a gap between the extremes of rather loose approximate point kinetics and rather tightly defined and too sophisticated industrial schemes. NDM is based on the 2-group diffusion theory and a lumped parameter model with maximized mesh size. It is validated here on an elementary CANDU-like LOCA benchmark proposed by AECL in the seventies. Chosen for its model simplicity, this design transient allows one to describe NDM principles and to carefully check the accuracy without any need for thermal calculations. Thus precise modeling of the strong coupling between neutronics and thermal–hydraulics is deferred for further developments, and simplified within this framework. Based on a simple transposition of the benchmark, a first application of NDM assesses safety of CANDU with “Th” fuel (Th/233U oxide) compared to “NU” (Natural Uranium oxide)