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Abstract In case of a core melt-down accident in a light water nuclear reactor, hydrogen is produced during reactor core degradation and released into the reactor building. This subsequently creates a combustion hazard. A local ignition of the combustible mixture may generate standing flames or initially slow propagating flames. Depending on geometry, mixture composition and turbulence level, the flame can accelerate or be quenched after a certain distance. The loads generated by the combustion process (increase of the containment atmosphere pressure and temperature) may threaten the integrity of the containment building and of internal walls and equipment. Turbulent deflagration flames may generate high pressure pulses, temperature peaks, shock waves and large pressure gradients which could severely damage specific containment components, internal walls and/or safety equipment. The evaluation of such loads requires validated codes which can be used with a high level of confidence. Currently, turbulence and steam effect on flame acceleration, flame deceleration and flame quenching mechanisms are not well reproduced by combustion models usually implemented in safety tools and further model enhancement and validation are still needed. For this purpose, two hydrogen deflagration benchmark exercises have been organised in the framework of the SARNET network. The first benchmark was focused on turbulence effect on flame propagation. For this purpose, three tests performed in the ENACCEF facility were considered. They concern vertical flame propagation in an initially homogenous mixture with 13 vol.% hydrogen content and different geometrical configurations. Three blockage ratios of 0, 0.33 and 0.6 were considered to generate different levels of turbulence. The second benchmark objective was the investigation of the diluting effect on flame propagation. Thus, three tests performed in the ENACCEF facility using the same blockage ratio of 0.63 and three different initial gas compositions (with 10, 20 and 30 vol.% diluents) have been considered. Since ENACCEF runs at ambient temperature, a surrogate to steam was used consisting of a mixture of 0.6He + 0.4CO 2 on molar basis. This paper aims to present the benchmarks conclusions regarding the ability of LP and CFD combustion models to predict the effect of turbulence and diluent on flame propagation.

Abstract The Antarctic and Greenland ice contains an almost direct record of past atmospheric CH 4 . The record over the last 200 years reveals a spectacular 150% increase of the CH 4 atmospheric mixing ratio since pre-industrial times. At the scale of a glacial-interglacial cycle the record shows a remarkable correlation with climatic changes, with high (low) CH 4 levels during warm (cold) periods. A striking feature of the glacial-interglacial CH 4 record is the presence of large and abrupt (at the scale of a century or less) changes during the last glaciation and glacial-interglacial transition. The classical interpretation for the origin of CH 4 changes prior to the industrial era involves mainly the wetland source. In the context of gas hydrates the question is to know whether the past ice-core record contains fingerprints of catastrophic hydrate release (CHR). We currently conclude that the available record shows no evidence for CHR but additional ice-core analyses are necessary to reach a more definitive conclusion.

This paper explores to what extent moving towards the 30% GHG emission reductions by 2020 with respect to 1990 in the EU can be considered a transformative target. To do so, we first define the concept of transformative targets from a complex systems perspective and show a novel approach and original results using an extended application of the GEM-E3 model. Traditional macroeconomic models cannot easily handle key synergetic system effects derived from green growth and sustainability policies, and thus require additional features. We analyse the role of semi-endogenous growth driven by learning-by-doing and low-carbon investment expectations following a long-term transformative trajectory.

Abstract. The increased resolution of numerical weather prediction models allows nowadays addressing more realistically urban meteorology and air pollution processes. This has triggered new interest in modelling and describing experimentally the specific features and processes of urban areas. Recent developments and results performed within the EU-funded project FUMAPEX on integrated systems for forecasting urban meteorology and air pollution are reported here. Sensitivity studies with respect to optimum resolution, parametrisation of urban roughness and surface exchange fluxes and the role of urban soil layers are carried out with advanced meso- or sub-meso meteorological models. They show that sensible improvements can be achieved by higher model resolution that is accompanied with better description of urban surface features. Recommendations, especially with respect to advanced urban air quality forecasting and information systems, are given together with an assessment of the needed further research and data.

CF4 is a strong greenhouse gas of both anthropogenic and natural origin [D.R. Worton et al., Environ. Sci. Technol. 41, 2184 (2007)]. However, high-resolution infrared spectroscopy of this molecule has received only a limited interest up to now. Until very recently, the public databases only contained cross-sections for this species, but no detailed line list. We reinvestigate here the strongly absorbing ν3 region around 7.8 μm. New Fourier transform infrared (FTIR) spectra up to a maximal resolution of 0.0025 cm−1 have been recorded: (i) room-temperature spectra in a static cell and (ii) a supersonic expansion jet spectrum at a 23 K estimated temperature. Following the work of Gabard et al. [Mol. Phys. 85, 735 (1995)], we perform a simultaneous analysis of both the ν3 and 2ν4 bands since a strong Coriolis interaction occurs between them, perturbing the ν3 R-branch rotational clusters around J = 20. Similarly to Gabard et al. , we also include ν4 FTIR data and microwave data in the fit. The analysis is pe...

AbstractProfessional and scientific networks built around the production of sweet cherry (Prunus avium L.) led to the collection of phenology data for a wide range of cultivars grown in experimental sites characterized by highly contrasted climatic conditions. We present a dataset of flowering and maturity dates, recorded each year for one tree when available, or the average of several trees for each cultivar, over a period of 37 years (1978–2015). Such a dataset is extremely valuable for characterizing the phenological response to climate change, and the plasticity of the different cultivars’ behaviour under different environmental conditions. In addition, this dataset will support the development of predictive models for sweet cherry phenology exploitable at the continental scale, and will help anticipate breeding strategies in order to maintain and improve sweet cherry production in Europe.