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

Analysis of Risks Associated with Hazardous Materials Transportation in the French Chemical Industry

This article focuses on the risks associated with Hazardous Materials Transportation (HazMaT) events in the French chemical industry between 1981 and 2022. The study aims to analyze and assess the causes and consequences of past events using the ARIA database, which lists over 54,000 events that have taken place in France and abroad. The severity of events is classified into five categories, from near misses to catastrophic events. The study highlights the importance of risk analysis/assessment and lessons learned from past events in managing natural and technological risks

Visibility Assessment of New Photovoltaic Power Plants in Areas with Special Landscape Value

Power plants based on renewable sources offer environmental, technical and economic advantages. Of particular importance is the reduction in greenhouse gas emissions compared to conventional power plants. Despite the advantages, people are often opposed to the construction of these facilities due to their high visual impact, particularly if they are close to places with a great cultural and/or landscape value. This paper proposes a new methodology for identifying the most suitable geographical areas for the construction of new photovoltaic (PV) power plants in zones of special scenic or cultural interest, helping to keep the environment free from the visual intrusions caused by these facilities. From several repeated analyses, the degree of visibility of the new PV plant, the potential observation time of passing visitors, considering the route they follow and their speed, and the increase in visibility of the plants when seen totally or partially with the sky as background, are determined. The result obtained is a map showing the ranking of the geographical areas based on a variable calculated in such analyses: the Global Accumulated Perception Time (GAPT). The application of this methodology can help the different agents involved in the decision-making process for the installation of new PV plant by providing them with an objective visibility criterion

The 2000 Tularemia Outbreak: A Case-Control Study of Risk Factors in Disease-Endemic and Emergent Areas, Sweden

A widespread outbreak of tularemia in Sweden in 2000 was investigated in a case-control study in which 270 reported cases of tularemia were compared with 438 controls. The outbreak affected parts of Sweden where tularemia had hitherto been rare, and these “emergent” areas were compared with the disease-endemic areas. Multivariate regression analysis showed mosquito bites to be the main risk factor, with an odds ratio (OR) of 8.8. Other risk factors were owning a cat (OR 2.5) and farm work (OR 3.2). Farming was a risk factor only in the disease-endemic area. Swollen lymph nodes and wound infections were more common in the emergent area, while pneumonia was more common in the disease-endemic area. Mosquito bites appear to be important in transmission of tularemia. The association between cat ownership and disease merits further investigation

Timing of treatment initiation for mild gestational diabetes mellitus and perinatal outcomes

To examine the association between gestational age (GA) at the time of treatment initiation for gestational diabetes (GDM) and maternal and perinatal outcomes

Effect of expanding vs. reducing vowel contrast on adaptation to altered auditory feedback

International audienceAbstract Speakers modify their speech in order to compensate for a perturbation in their auditory feedback. Auditory-motor adaptations can be studied by applying specific real time perturbations to a speaker's auditory feedback. For example, when a speaker produces vowels, it is possible to change the value of the first formant (F1) in the acoustic signal and to play it back in real time to the speaker through headphones. Speakers learn to compensate for this perturbation by changing F1 in their production in a direction opposite to the perturbation [1, 2, 3]. This compensation lasts for a period of time after the perturbation is removed, which shows that motor learning occurred. Most of the studies on the adaptation of F1 perturbations have used a single perturbation consisting of either increasing or decreasing F1 in speakers' auditory feedback. Recently [4], using a similar protocol, we showed that speakers can also simultaneously learn several auditory-motor transformations when each perturbation is applied to the production of a vowel in a given word. Hence, when speakers are trained to produce the words "head" and "had" repetitively and in random order, receiving an upwards perturbation of F1 for "head" and a downwards perturbation for "had", they progressively decrease the F1 value in their "head" productions while at the same time, they increase the F1 value in "had" . We interpreted these results as evidence that motor learning in speech is linked to a given word or that sensori-motor learning is quite specific. The method we developed (applying different perturbations to different vowels in a same training session) is also a way to modify the contrast between two utterances in subjects' auditory feedback. For example, when F1 is shifted upwards in "head" and downwards in "had", this makes the auditory feedback of "head" and "had" more similar. In contrast, the reverse perturbations make the two utterances more distinct. Hence, in our previous work, the adaptations observed could also be interpreted as an effort to preserve "head"-"had" contrast. In the current study, we re-analyzed the adaptations that we observed in our previous work as a change in the F1-F2 distance between the two vowels, rather than an adaptation of F1 for each vowel. We also compared these adaptations to those of two other groups of speakers trained in similar conditions but received perturbations only for "head" utterances, not for "had" (which is another way to change "head"-"had" contrast). We observed that, as in our previous results, subjects learnt to change the motor control for each utterance in different ways. However, analysing the adaptation in term of relations between the two words shows that speakers also adapt to maintain the contrast between the two utterances. Thus, speech-specifics constraints, such as contrast between two target sounds, also play a role in auditory-motor adaptation. References [1] Houde JF and Jordan MI (2002). Sensorimotor adaptation of speech I: Compensation and adaptation. Journal of Speech and Hearing Language. 45, 295 - 310. [2] Purcell, D.W. and Munhall, K.G. (2006). Adaptive control of vowel formant frequency: Evidence from real-time formant manipulation. Journal of the Acoustical Society of America, 120, 966-977. [3] Villacorta VM, Perkell JS et Guenther FH (2007). Sensorimotor adaptation to feedback perturbations of vowel acoustics and its relation to perception. Journal of the Acoustical Society of America;122(4):2306-19. [4] Rochet-Capellan A, Ostry DJ (2011). Simultaneous acquisition of multiple sensorimotor transformations in speech. Journal of Neuroscience, 31:2648-2655

Generalization of auditory-motor learning in speech

International audienceDoes motor learning generalize to new situations that are not experienced during training, or is motor learning essentially specific to the training situation? In the present experiments, we use speech production as a model to investigate generalization in motor learning. We tested for generalization from training to transfer utterances by varying the acoustical similarity between these two sets of utterances. During the training phase of the experiment, subjects received auditory feedback that was altered in real time as they repeated a single Consonant-Vowel-Consonant (CVC) utterance. Different groups of subjects were trained with different CVC utterances, which differed from a subsequent transfer utterance in terms of the initial consonant or vowel. During the adaptation phase of the experiment, we observed that subjects in all groups progressively changed their speech output to compensate for the perturbation (altered auditory feedback). After learning, we tested for generalization by having all subjects produce the same single transfer utterance while receiving unaltered auditory feedback. We observed limited transfer of learning, which depended on the acoustical similarity between the training and the transfer utterances. The gradients of generalization observed here are comparable to those observed in limb movement. The present findings are consistent with the conclusion that speech learning remains specific to individual instances of learning

Design of a Fast Molten Salt Reactor for Space Nuclear Electric Propulsion

International audienceThe French National Center for Scientific Research (CNRS) is carrying out design studies on a nuclear electric propulsion (NEP) engine based on a molten salt reactor (MSR). A NEP engine based on liquid nuclear fuel could allow developing a core design with relatively high power densities and temperatures while using simple reactivity control systems and keeping low pressure and temperature gradients in the fuel. Nevertheless, the design work of such an engine poses significant technical challenges and requires the use of advanced numerical simulation tools. Different MSRs for space are currently being studied. In this work, a MSR concept using a fast neutron spectrum is investigated using a multiphysics tool based on a numerical coupling between the OpenFOAM (computational fluid dynamics) and SERPENT 2 (Monte Carlo neutronics) codes. The analysis of this paper is focused on the reactor core coupled neutronic and thermal-hydraulic phenomena. Steady state full-power conditions are calculated for two different fast MSR designs using low-enriched uranium (LEU) and highly enriched uranium. The results show that the proposed core layout and materials allow obtaining a satisfactory temperature distribution in the core (maximal values and gradients) without significant penalization of the reactor operating conditions. A reactivity control strategy excluding the use of control rods is studied for the LEU concept. Transient and safety studies are also performed and show acceptable performance

Take a breath and take the turn: how breathing meets turns in spontaneous dialogue

International audiencePhysiological rhythms are sensitive to social interactions and could contribute to defining social rhythms. Nevertheless, our knowledge of the implications of breathing in conversational turn exchanges remains limited. In this paper, we addressed the idea that breathing may contribute to timing and coordination between dialogue partners. The relationships between turns and breathing were analysed in unconstrained face-to-face conversations involving female speakers. No overall relationship between breathing and turn-taking rates was observed, as breathing rate was specific to the subjects' activity in dialogue (listening versus taking the turn versus holding the turn). A general inter-personal coordination of breathing over the whole conversation was not evident. However, specific coordinative patterns were observed in shorter time-windows when participants engaged in taking turns. The type of turn-taking had an effect on the respective coordination in breathing. Most of the smooth and interrupted turns were taken just after an inhalation, with specific profiles of alignment to partner breathing. Unsuccessful attempts to take the turn were initiated late in the exhalation phase and with no clear inter-personal coordination. Finally, breathing profiles at turn-taking were different than those at turn-holding. The results support the idea that breathing is actively involved in turn-taking and turn-holding