Predicting leakage of the VERCORS mock-up and concrete containment buildings - a digital twin approach

EDF operates a nuclear power generation fleet made up of 56 reactors. This fleet contains 24 reactors designed as double-walled concrete containment building. The inner concrete containment vessel has no metallic liner and is a prestressed reinforced concrete building. The inner concrete containment vessel is designed to withstand a severe accident, in terms of mechanical and sealing behaviour. The tightness of the containment is tested every 10 years, by carrying out a pressurization test and by measuring the leak rate. The leak rate is required to be below a regulatory threshold to continue operation of the concrete containment building for the next ten years. Ageing of concrete due to drying, creep and shrinkage leads to increase prestress loss and then leak rate with time. For some containment buildings, the leak rate gets closer to the regulatory threshold with time, so important coating programs are planned to mitigate and limit the leak rate under the regulatory threshold. Therefore, it is very important for EDF to have a concrete containment building leak rate prediction tool. To address this issue, an important research program around a 1/3 scale concrete containment building mock-up called "VERCORS" have been launched at EDF. The mock-up is heavily instrumented, and its materials (concrete, prestressing cables) have been widely characterized and studied. An important numerical effort has also been made to implement structural computations of the mock-up and to capitalize these computations as well as their post-processing (so as to compare automatically with the monitoring data) in what can be called a digital twin of the mock-up. This digital twin is now used to predict the leakage of VERCORS mock-up before yearly pressure test, and also to optimize the repair programs on the real containments

Identifying cost-competitive greenhouse gas mitigation potential of French agriculture

The agriculture, forestry and other land use sector are responsible for 24% (10–12 Pg CO2e per year) of anthropogenic greenhouse gas (GHG) emissions worldwide, with concomitant opportunities for mitigation. A scientific panel used deliberative methods to identify ten technical measures comprising 26 sub-measures to reduce GHG emissions from agriculture in France. Their abatement potential and cost are compared. The proposed measures concern nitrogen (N) management, management practices that increase carbon stocks in soils and biomass, livestock diets, and energy production and consumption on farms. Results show that the total abatement potential can be divided into three parts. One third of the cumulated abatement potential corresponds to sub-measures that can be implemented at a negative technical cost. These sub-measures focus on increased efficiency in input use including N fertilisers, animal feed and energy. The second third are sub-measures with moderate cost (€25 per metric Mg of avoided CO2e). These require investment with no direct financial return, the purchase of particular inputs, dedicated labour time or involve production losses. Assuming additivity, the cumulated abatement is 32.3 Tg CO2e per year in 2030, but only 10 Tg (i.e. 10% of current agricultural emissions) when calculated under current inventory rules. This study confirms that a significant abatement potential exists in the agricultural sector, with two thirds of this potential at low or even negative cost. This is likely to be an underestimated as it is based on a status quo of the current agricultural system. Results also emphasise the need to upgrade inventory rules so that efforts to reduce emissions can be accounted for

MAORY for ELT: preliminary design overview

MAORY is one of the approved instruments for the European Extremely Large Telescope. It is an adaptive optics module, enabling high-angular resolution observations in the near infrared by real-time compensation of the wavefront distortions due to atmospheric turbulence and other disturbances such as wind action on the telescope. An overview of the instrument design is given in this paper

The MAORY first-light adaptive optics module for E-ELT

The MAORY adaptive optics module is part of the first light instrumentation suite for the E-ELT. The MAORY project phase B is going to start soon. This paper contains a system-level overview of the current instrument design

A Solid Oxide Fuel Cell Operating in Gradual Internal Reforming Conditions under Pure Dry Methane

International audienceA planar solid oxide fuel cell (SOFC) was designed to be operated in gradual internal reforming conditions under pure dry methane. Stable operation was achieved for about 30 h. This result was obtained by deposition onto a Ni–yttria-stabilized zirconia cermet of a highly active and carbon-deposition-resistant catalyst layer consisting of Ir/CeO2. The performances of this layer were first evaluated in situ at open-circuit voltage, and then the principle of gradual internal reforming associated with electrocatalytic dissociation was demonstrated. The best cell performances with CH4/H2O=1/4 were 0.1  A  cm−2 at 0.55 V (about 55  mW cm−2) at 1173 K

Direct methane solid oxide fuel cell working by gradual internal steam reforming: Analysis of operation

International audienceA solid oxide fuel cell was designed to be operated with pure hydrocarbons, without additive or carrier gas, in order to bring technological simplifications, cost reductions and to extend the fuel flexibility limits. The cell was built-up from a conventional cell (LSM/YSZ/Ni-YSZ), to which was added a Ir–CeO2 catalyst layer at the anode side and an original current collecting system. The cell was first operated with steam in gradual internal reforming (GIR) conditions (R = [H2O]/[CH4] −2 at max power for 120 h. Small but abrupt deterioration of the performances was observed, but no carbon deposition. Electrical and chemical analysis of this degradation are provided.At total, the fuel cell was operated for more than 200 h in pure dry methane, demonstrating that gradual internal reforming actually occurred efficiently in the anode compartment, which make possible operation without reforming agent such as H2O or CO2 for other hydrocarbon fuels

Le traçage isotopique pour étudier la production par les microorganismes du sol d'oxyde nitreux, gaz à effet de serre.

6 pagesNational audienc

Influence de l'apport d'amendements organiques sur les émissions de N2O et de N2 par les sols, au cours de la dénitrification, révélée par le traçage isotopique 15

International audienc

Emissions and spatial variability of N2O, N2 and nitrous oxide mole fraction at the field scale, revealed with 15N isotopic techniques.

11 pagesInternational audienceThe accurate measurement of nitrous oxide (N2O) and dinitrogen (N2) during the denitrification process in soils is a challenge which will help to estimate the contribution of soil N2O emissions to global warming. Oxygen concentration, nitrate concentration and carbon availability are generally the main factors that control soil denitrification rate and the amount of N2O orN2 emitted. The aim of this paper is to present a database of the N2O mole fraction measured at the field scale, and to test hypotheses concerning its regulation. A 15N-nitrate tracer solution was added to 36 undisturbed soil cores on a 20 m!20 m cultivated field plot. Fluxes of CO2, N2O and N2 from the soil surface were monitored for 24 h. Soil moisture, bulk density, carbon, nitrogen and mineral nitrogen concentration were also measured to investigate possible spatial relationships between their variations and those of N2O, N2 and nitrous oxide mole fraction. Under high water content, nitrous oxide and N2 emissions were highly variable with variation coefficients of 70–140%. N2O emission rates were about twice as high as those of N2, with a total denitrification rate ranging from 269 to 3843 g N ha-1 d-1. After 24 h of incubation, the values of nitrous oxide mole fraction ranged from 0.15 to 0.94 and no significant decline during incubation time was observed. Spatial variability of N2O, N2 and nitrous oxide mole fraction was high and no spatial dependence was observed at the scale of the experimental plot. Only tenuous relationships between gaseous nitrogen emissions and soil properties (mainly nitrate concentration and moisture content) were found. Meanwhile, a positive correlation was observed between N2 and CO2 emissions. This result supports the hypothesis that an increase in soil available organic carbon leads to N2 emissions as the end product of denitrification