Strain-induced crystallization in sustainably crosslinked epoxidized natural rubber

International audienc

Parametric Studies on Heterogeneous Cores for Fast Breeder Reactors: The Pre-Racine and Racine Experimental Programs

International audienceritical assembly at Cadarache since 1976, were designed for the study of the neutron physicscharacteristics of heterogeneous fast reactor cores. Geometrically simple configurations were chosenin which parameters, being typical for heterogeneous cores, were varied in a systematic manner whilethe basic fissile composition was kept the same.Measurements were made especially of the critical mass, the distributions of reaction rates andthe spectral indices, the reactivity of sodium voiding, and control rod worths. Analyses were madeindependently by Commissariat a VEnergie Atomique (CEA) and DEBENE using their own calculationaltechniques and cross sections. No bias for core heterogeneity was found on critical mass predictions.The CEA calculations for void reactivities are consistent in heterogeneous and homogeneousconfigurations.For the calculation of local parameters, e.g., reaction rates and spectral indices, moresophisticated methods must be applied in heterogeneous cores, as transport effects also become moreimportant in fissile zones with increasing fertile volume fraction.It was found at CEA that the ratio of the calculated reactivity of a central control rod to the experimentalvalue does not change with the core size or with the presence of internal breeder zones

A review on self-healing polymers for soft robotics

The intrinsic compliance of soft robots provides safety, a natural adaptation to its environment, allows to absorb shocks, and protects them against mechanical impacts. However, a literature study shows that the soft polymers used for their construction are susceptible to various types of damage, including fatigue, overloads, interfacial debonding, and cuts, tears and perforations by sharp objects. An economic and ecological solution is to construct future soft robotic systems out of self-healing polymers, incorporating the ability to heal damage. This review paper proposes criteria to evaluate the potential of a self-healing polymer to be used in soft robotic applications. Based on these soft robotics requirements and on defined performance parameters of the materials, linked to the mechanical and healing properties, the different types of self-healing polymers already available in literature are critically assessed and compared. In addition to a description of the state of the art on self-healing soft robotics, the paper discusses the driving forces and limitations to spur the interdisciplinary combination between self-healing polymer science and soft robotics

Challenges in Containment Thermal Hydraulics

The containment of a nuclear reactor is a component whose loss in an accident has serious consequences on property, persons, and environment. The Fukushima accident reminded us of this reality. For more than 30 years, the French Nuclear Energy and Alternative Energies Commission has been conducting research on the failure modes of these enclosures, particularly on their slow pressurization during a steam release and hydrogen risk. Significant progress has been made on wall condensation and its spatial distribution, the occurrence and erosion of gas stratification, and the impact of mitigation systems, such as spraying and catalytic recombiners. This knowledge has been included in numerical tools and internationally recognized expertise. These tools have also been used for the safety of the hydrogen energy industry. The emergence of new systems, particularly passive systems and new light water reactor concepts, has led us to examine new questions that will have to be addressed in the coming years. This examination is done in view of current computational fluid dynamics code capabilities and limitations

A educação infantil e a questão da escola: o caso da França

Nos últimos trinta anos, a prioridade dada a uma lógica escolar para justificar a pré-escola coincide com uma dupla mudança na instituição. A primeira diz respeito às relações que a escola maternal mantém com a escolarização obrigatória e com as estruturas de cuidados para as crianças pequenas. A outra refere-se às reformas do currículo escolar e ao desenvolvimento dos processos de avaliação. A escola maternal, local de acolhimento, de cuidados e de preparação para a escola, tornou-se institucionalmente uma verdadeira escola. A difusão das comparações internacionais contribuiu para essas mudanças