Rescoll (France)

The concept of a safe geological repository for managing radioactive waste relies on a multi-barrier system comprising both the host rock and various engineered barriers, these latter being referred to as the engineered barrier system (EBS). The robustness of the EBS depends directly on the materials used, which play a crucial role in ensuring its performance. These materials must demonstrate exceptional durability, stability, and compatibility with the host rock and the types of waste expected in the future repository. Moreover, they must remain intact over timescales ranging from hundreds to thousands of years, depending on the repository’s design.Regardless of the repository concept, a disposal container is required to encase the primary HLW package. Currently, reference materials are primarily metals such as steel or copper. In the case of steel, particularly carbon steel, one significant drawback is the production of H₂(g) during corrosion under anoxic conditions. Minimising or eliminating this phenomenon would facilitate easier and even safer waste management within the disposal facility. This issue is a key motivation for exploring alternative solutions, such as ceramic materials, which do not generate gas when altered.Research on ceramics as alternatives to metals began in the late 1970s and has periodically regained interest. However, the topic has largely been addressed conceptually, with few concrete research programmes dedicated to tackling this challenge. Since the mid-2000s, Andra has initiated a long-term R&D programme to assess the technical feasibility of a ceramic HLW container that meets the safety requirements of the Cigéo repository concept.This presentation aims to provide an overview of global research activities related to ceramic options for HLW containers, with a particular focus on the Cigéo concept. Both bulk ceramics and ceramic coatings will be considered. The advantages and limitations of these solutions will be discussed, along with potential approaches to address identified challenges. It is important to note that this contribution does not seek to provide exhaustive details on all related topics but rather offers a scientific and technical overview of ongoing work in this field, which may be of interest to stakeholders in the field of radioactive waste geological disposal.

ABSTRACTBackgroundPharyngoCutaneous Fistulae (PCF) represent a significant clinical challenge in otorhinolaryngology practice. The use of biomaterials could improve outcomes or even replace the use of a flap in pharyngolaryngeal surgery.MethodsThis systematic review included all studies evaluating the application of biomaterials for the prevention of PCF after pharyngeal surgery.ResultsA total of 19 articles (12 clinical and 7 animal studies) were included. They assessed the use of a biomaterial to cover mucosal sutures (n = 15) or to replace a mucosal defect and guide secondary healing (n = 4). Most studies evaluated commercialized biomaterials (n = 11) rather than experimental devices (n = 5) or platelet‐derived autologous medical devices (n = 4).ConclusionThere are already strong arguments to support the use of several biomaterials to cover pharyngeal sutures in order to decrease the rate of PCF after TL or TPL. Replacing a pharyngeal mucosal defect by a biomaterial is currently a more elusive goal.

Corrosion is a major threat in the aeronautic industry, both in terms of safety and cost. Efficient, versatile, and cost affordable solutions for corrosion monitoring are thus needed. Ultrasonic Lamb Waves (LW) appear to be very efficient for corrosion monitoring and can be made cost effective and versatile if emitted and received by a sparse array of piezoelectric elements (PZT). A LW solution relying on a sparse PZT array and allowing to monitor µm-sized corrosion pit growth on stainless 316L grade steel plate is here evaluated. Experimentally, the corrosion pit size is electrochemically controlled by both the imposed electrical potential and the injection of a corrosive NaCl solution through a capillary located at the desired pit location. In parallel, the corrosion pit growth is monitored in-situ every 10 s by sending and measuring LW using a sparse array of 4 PZTs bonded to the back of the steel plate enduring corrosion. As a ground truth information, the corrosion pit volume is estimated as the dissolved volume balancing the electronic charges exchanged during corrosion. The corrosion pit radius is additionally checked post-experiment precisely with an optical measurement. Measured LW signals are then post-processed in order to compute a collection of synthetic damage indexes (DIs). After dimension reduction steps, obtained DI values correlates extremely well with the corrosion pit radius. Using a linear model relating those DI values to corrosion pit radius, it is demonstrated that corrosion pit from 30 µm to 150 µm can be reliably detected, located, and their upcoming size extrapolated. Two independent experiments were achieved in order to ensure the repeatability of the proposed approach. LW managed by a sparse PZT array thus appears to be reliable and efficient to monitor growth of µm-sized corrosion pits on 316L steel plates. If embedded in aeronautical structure, such an approach could be a versatile and cost-effective alternative to actual non-destructive maintenance procedures that are time and manpower consuming.

Vascular grafts made of synthetic polymers perform poorly in cardiac and peripheral bypass applications. In these applications, chitosan-based materials can be produced and shaped to provide a novel scaffold for vascular tissue engineering. The goal of this study was to evaluate in vitro the mechanical properties of a novel chitosan formulation to assess its potential for this scaffold. Two chitosan-based hydrogel tubes were produced by modulating chitosan concentration. Based on the standard ISO 7198:1998, the hydrogel tubes were characterized in vitro in terms of suture retention strength, tensile strength, compliance, and burst pressure. By increasing chitosan concentration, suture retention value increased to reach 1.1N; average burst strength and elastic moduli also increased significantly. The compliance seemed to exhibit a low value for chitosan tubes of high concentration. By modulating chitosan concentration, we produced scaffolds with suitable mechanical properties to be implanted in vivo and withstand physiological blood pressures.