CEA Le Ripault

The use of lithium-ion (Li-ion) batteries has rapidly increased due to improvements in performance, durability, and cost-effectiveness, driven by the growth of electric vehicles (EVs), renewable energy storage, and portable electronics. However, the safety of Lithium-ion batteries remains a major concern due to the risk of thermal runaway, which can result in fast heat release, the ejection of particles and gases, and possibly fire and explosion. Therefore, the reliable characterization of thermal runaway energy and gas volume release is essential. In this study, 29 thermal runaway tests of large-capacity prismatic and pouch NMC (Nickel Manganese Cobalt oxide cathode) cells were analysed. Thermal runaway energy, normalized by the electrical energy of the cell at the time thermal runaway occurs, was constant and equal to 1.25 during all the tests performed under vacuum and inert atmosphere. Similarly, the normalized number of moles generated during thermal runaway remained constant at 4.9 × 10 -3 mol·kJ -1 . When the tests were conducted in air, the large quantity of oxygen available led to additional combustion and energy release. The normalized thermal runaway energy increased to 5.0, while the normalized average number of moles decreased to 4.2 × 10 -3 mol·kJ -1 . Thermodynamic equilibrium calculations of vented gas combustion with air show that gas phase combustion alone does not explain this energy increase, the contribution of graphite is therefore demonstrated. The two conditions-under vacuum and in air- represent the two limiting cases of air access in a typical battery module, therefore the data presented in this work can be useful for evaluating thermal runaway propagation and casing integrity in a battery module during the design phase. • Thermal runaway energy is proportional to the embedded electrical energy • Number of gas moles releases is proportional to the embedded electrical energy • Tests in air released four times more energy compared to an inert atmosphere • Gas phase combustion alone does not account for the increase in energy release • Graphite combustion can significantly contribute to the total energy release

ABSTRACT Impact experiments carried out at very low speeds on a target consisting of an HMX‐based explosive protected by a thin steel case have recently been published. Reactions are observed for projectiles of a few kilograms and impact speeds of the order of meters per second. These impacts are simulated using finite elements, with a Lagrangian solver and an h‐adaptive mesher. The thermal and mechanical fields are solved at the scale of the structure. The influence of potential sources of heating, such as friction at the projectile/case interface, heating of the projectile itself, and heating by plastic dissipation of the case and the explosive, is studied. For the latter mechanism, heat is assumed to come from the plastic dissipation of HMX crystals. The results show that the geometric configuration of these tests, including the shape of the projectile, leads to a strong deformation of the explosive. The transfer of heat generated by other mechanisms could be neglected.

Retrospective translational analyses have shown a high rate of false negatives between clinical thorough QT studies (TQT) and preclinical cardiovascular safety pharmacology studies. The aim of this work was to model the results of clinical TQT studies from cardiovascular safety pharmacology studies conducted on a large set of reference drugs in beagle dogs by implanted telemetry. All preclinical studies were based on a standard four-animal crossover design comparing the vehicle to the reference drug. The model used was based on the one-step QTc correction model. This model was adapted in order to apply the same statistical method in preclinical studies as in clinical trials. The sensitivity of the model made it possible to detect QTc prolongation of at least 5 ms with all reference hERG blockers known to cause QT prolongation in humans. Modelling of moxifloxacin (10 mg/kg, po) effects was in agreement with data published from clinical TQT studies with moxifloxacin 400 mg showing a QTc prolongation greater than 5 ms between 1 and 4 hours post-dose. This study shows a noticeable reduction in the risk of false negatives with several references drugs associated with a phenomenon of concealed QTc prolongation. Moreover, several reference drugs did change the slope of the QT/HR slope justifying the principles of the one-step QTc model. Modelling results of TQT studies with the one-step QTc model for applying the same statistical approach as in the clinic can improve the translational value of preclinical cardiovascular safety pharmacology studies and reduce the risk of false negatives.

main: 19 pages, 3 figures. Supplemental: 3 pages, 2 figures

International audience

The goal of the European plasma Volumetric Neutron Source (VNS), which is a 14 MeV n-source, is to test and validate technological solutions of breeding blankets in an environment representative of a future fusion power plant such as DEMO. One of the assessed magnetic configurations is a tokamak device with a radius of ≈ 2.5 m that produces a D-T fusion power of ≈ 30 MW. The architecture of VNS integrates a single null divertor located at the bottom of the vacuum vessel. The ITER-like divertor is designed to be actively water-cooled for stationary operation and is made up with 36 cassette modules. Each module has a cassette body with a set of plasma facing components (PFCs) with tungsten as plasma facing material. The PFC arrangement is a dome positioned in the central part with reflector plates on both sides located between inboard and outboard target striking surfaces. The selected PFC technological solutions are: the plasma facing units (PFUs) of the targets are armored with tungsten monoblocs bonded onto a cooling pipe made of CuCrZr with an inserted twisted tape, the PFUs of the dome are made up with tungsten flat tiles bonded onto a CuCrZr hypervapotron cooling structure. This paper presents the status of the development of the divertor conceptual design. Preliminary analyses confirmed that the design is compatible with plasma scenarios foreseen for VNS operation.

Gurney velocity (uG) and cylinder wall velocity (vs) of energetic materials are calculated using the semi-empirical Cγ method, an analytical model previously developed for CHNO high explosives and presently extended to additional elements and to explosives at low loading density. The results are compared to recent procedures based on thermochemical simulations. Regarding uG, both approaches perform similarly well for organic high explosives, with an average relative error close to 2.6%. However, Cγ underestimates uG for tritonal, an explosive with 20-40 wt% aluminium powder. Regarding vs, a newly introduced empirical equation is shown to perform better than the Gurney model, although not as well as a recent correlation involving the detonation energy derived from thermochemical simulations, which are still required to predict cylinder wall velocities with optimal accuracy. With regard to the application of present models to the design of new materials, Cγ is not recommended for metal-containing compounds. However, for the high-thoughput design of organic high explosives, it is an invaluable tool allowing fast and reproducible calculations of Gurney energies with state-of-the-art accuracy. A very simple, hackable Python script is provided for this purpose as supplementary information.

A systematic study of nitration of (hetero)arenes was conducted using HTE. The generated data were used to develop a predictive tool relying on machine learning to evaluate the best reaction conditions depending on the targeted substrate.

The effect of dimethyl phthalate (DMP) contamination on the optical properties of wave plates fabricated by Glancing Angle Deposition are investigated. A long-term reduction of transmission and retardance is observed associated with DMP sorption.