Search

The EU conducted the pre-conceptual design (PCD) phase of the demonstration reactor (DEMO) during 2014–2020 under the framework of the EUROfusion consortium. The current strategy of DEMO design is to bridge the breeding blanket (BB) technology gaps between ITER and a commercial fusion power plant (FPP) by playing the role of a “Component Test Facility” for the BB. Within this strategy, a so-called driver blanket, with nearly full in-vessel surface coverage, will aim at achieving high-level stakeholder requirements of tritium self-sufficiency and power extraction for net electricity production with rather conventional technology and/or operational parameters, while an advanced blanket (or several of them) will aim at demonstrating, with limited coverage, features that are deemed necessary for a commercial FPP. Currently, two driver blanket candidates are being investigated for the EU DEMO, namely the water-cooled lithium lead and the helium-cooled pebble bed breeding blanket concepts. The PCD phase has been characterized not only by the detailed design of the BB systems themselves, but also by their holistic integration in DEMO, prioritizing near-term solutions, in accordance with the idea of a driver blanket. This paper summarizes the status for both BB driver blanket candidates at the end of the PCD phase, including their corresponding tritium extraction and removal (TER) systems, underlining the main achievements and lessons learned, exposing outstanding key system design and R&D challenges and presenting identified opportunities to address those risks during the conceptual design (CD) phase that started in 2021.

This work presents the results of the implementation in the GEneral Tokamak THErmal-hydraulic Model of available models for the generation and transport of any dispersed material in flowing PbLi eutectic mixture. In particular, the focus is on Activated Corrosion Products circulating as solid suspension in the PbLi loop of the Water-Cooled Lithium-Lead Breeding Blanket of the EU DEMO fusion reactor. A simple test case is used to show that the distribution of the concentration of activated corrosion products at any point of the PbLi loop, both in the water-cooled lithium-lead breeding blanket and in the related ITER Test Blanket System, can be determined by the model. Moreover, thanks to the model’s dynamic nature, operational transients can be simulated; for instance, starting from zero impurities in the PbLi alloy, the evolution of the concentration of corrosion products is shown, until the steady-state is reached. The results obtained with this tool can be useful not only for radiological safety purposes, but also because activated corrosion products may affect the PbLi flow itself and the efficiency of the tritium removal system, with consequences on the achievable Tritium Breeding Ratio. A rigorous verification of the model is also performed.

In the European fusion programme, the Water Cooled Lithium Lead breeding blanket (WCLL BB) uses EUROFER as a structural material cooled with water at temperatures between 295 °C–328 °C and a pressure of 155 bar. The WCLL BB will be significantly irradiated (>2 dpa), while some parts will not receive significant heat loads, e.g. the sidewalls or the back-supporting structures. The irradiation, together with the irradiation temperature of EUROFER below 350 °C, produces a shift of the ductile-to-brittle-transition temperature (DBTT) to levels above room temperature at neutron doses, causing material damage as low as 2–3 dpa. Even though the DBTT does not reach the operating temperature level, brittle/non-ductile fracture is a concern during in-vessel maintenance when the BB temperature is below the DBTT. Two loading scenarios were identified as severe in this respect: (i) re-pressurization of the WCLL BB cooling loop after in-vessel maintenance, and (ii) dead weight loads during lifting of the BB segment. The embrittlement of the WCLL BB was investigated by quantifying the local DBTT shift in its parts based on current knowledge of the embrittlement behaviour of EUROFER under neutron irradiation. Therefore, a suitable, not overly conservative procedure was derived considering dpa damage and transmuted helium effects. The results demonstrate the ability to identify the 3D spread of the severely embrittled zones in the structure whose impact on the structural integrity was assessed considering the risk of brittle/non-ductile fracture. Thereby, the fracture mechanics approach established in nuclear codes was applied assuming its applicability to EUROFER. The embrittled zones in the first wall (FW) and its sidewalls pass the criteria when assessing the relatively low stresses resulting from the coolant pressure. The assessment was then continued considering stresses appearing in the FW during maintenance, in particular, when lifting the BB segment and transporting it out of the vacuum vessel. In this context, the maximum tolerable flaw sizes were determined in a parameter study considering designs of the FW with different cooling channel wall thicknesses.

There are few studies focused on spore and pollen clumps in paleopalynological samples, and these are only reports from the Northern Hemisphere. These aggregates may be of animal or floral origin. The goal of this contribution is to provide the first detailed study of spore and pollen clumps from the Southern Hemisphere, and to discuss their possible origin, botanical affinities, and pollination modes, based on their morphological characteristics, preservation and comparison with putative living representatives. Three fern spore clumps and 18 angiosperm pollen clumps were recognized in Maastrichtian-Danian La Colonia Formation sediments that outcrop at Chubut Province, Patagonia, Argentina. Most clumps are monospecific and composed of undamaged elements but some of them have two types of spore/pollen with corroded and/or fragmented exines. These findings represent the most diverse and abundant record of fern and angiosperm clumps from the Late Cretaceous and early Paleocene so far known from South America and the Southern Hemisphere. These results are indicative of the need for comprehensive large-scale studies on pollination of modern taxa and careful processing of palynological samples to lessen the already large bias in paleopalynological interpretations. The paucity of information on clumps in the fossil record has impaired our comprehension of dispersion/pollination in deep time. Keywords Floral origin * Coprolites * Monospecific clumps * Pollination modes Hay pocos estudios enfocados en agregados de esporas y polen procedentes de muestras palinologicas, y estos han sido reportados unicamente en el Hemisferio Norte. Estos agregados pueden ser de origen animal o floral. El objetivo de esta contribucion es proveer el primer estudio detallado de agregados de esporas y polen del Hemisferio Sur, y discutir sus posibles origenes, afinidades botanicas y modos de polinizacion, basados en sus caracteristicas morfologicas, preservacion y comparacion con posibles analogos modernos. Tres agregados de esporas de helechos y 18 de polen de angiospermas fueron reconocidos en los sedimentos del Maastrichtiano-Daniano de la Formacion La Colonia, aflorantes en la Provincia de Chubut, Patagonia, Argentina. La mayoria de los agregados son monoespecificos y estan compuestos por elementos en general bien preservados, aunque algunos tienen dos tipos de esporas/polen con exinas corroidas y/o fragmentadas. Estos hallazgos constituyen el registro mas diverso y abundante de agregados esporopolinicos del Cretacico Tardio y Paleoceno temprano de Sudamerica y del Hemisferio Sur. Los resultados de este trabajo indican la necesidad de realizar estudios exhaustivos a gran escala sobre polinizacion en taxones modernos y de desarrollar nuevas tecnicas palinologicas menos destructivas que permitan recuperar los agregados de las paleoasociaciones. Claramente, la escasez de informacion sobre agregados polinicos en el registro fosil afecta nuestra interpretacion acerca de la dispersion/polinizacion y su evolucion en el tiempo. Palabras clave Origen floral * Coprolitos * Agregados monoespecificos * Modos de polinizacion, Introduction Pollen and spores have major roles in plant sexual reproduction as they are fundamental to maintaining plant populations and successfully colonizing of new habitats. Floral and pollen traits are [...]

Background The predictive role of blood pressure variability for all‐cause mortality and fatal and nonfatal cardiovascular events has been described in the general population and in patients with diabetes, independently of mean BP. Although systolic blood pressure variability has been proposed as an informative measure for predicting clinical outcomes in patients with chronic kidney disease, its role in kidney transplant recipients is still debatable. Methods and Results We performed a retrospective, observational, monocentric analysis of all kidney transplant recipients in follow‐up at the outpatient Nephrology Clinic of San Martino Hospital from January 1, 2016 to December 31, 2016, who underwent kidney transplantation >12 months. The primary outcome was a fatal or nonfatal cardiovascular event (myocardial infarction, unstable angina, stroke, and hospitalization for heart failure). Visit‐to‐visit systolic blood pressure variability was expressed as the SD of systolic blood pressure values recorded at baseline and 3 months up to 18 months. Among the 272 patients (mean age, 64±13; 63% men) included in the present analyses, for each increase of 2.7 mm Hg in systolic blood pressure SD, the risk for events increased 3‐fold (hazard ratio [HR], 3.1 [95% CI, 1.19–7.88]; P=0.02), and patients in the highest tertile of systolic blood pressure SD showed a 4‐fold increased risk (HR, 4.1 [95% CI, 1.34–12.43]; P=0.01). This relationship was maintained even after incremental adjustment for time‐averaged pulse pressure, age, diabetes, and prior cardiovascular event (HR, 3.2 [95% CI, 1.1–10.0]; P=0.04). Conclusions Long‐term blood pressure variability represents a risk factor for cardiovascular events in kidney transplant recipients, even independently by several confounding factors including blood pressure load.

Two-dimensional transthoracic echocardiography (2D TTE) and two-dimensional transesophageal echocardiography (2D TEE) are regarded as the main imaging techniques for the assessment of degenerative mitral valve regurgitation (DMVR). However, describing the complex morphology of DMVR with 2D TTE and 2D TEE remains at the very least challenging. Three-dimensional (3D) TEE is an ideal technique for illustrating the extremely variable morphology of DMVR, providing images of unparalleled quality in terms of anatomical detail. In this review, we describe the key role of 3D TEE in various morphological scenarios that reflect everyday experiences in an echocardiographic laboratory. We also discuss the growing role of 3D TEE in mitral valve (MV) transcatheter edge-to-edge repair (TEER) and new modalities such as photorealistic and transparent displays, surface rendering parametric color maps, new algorithms for MVR quantification, and the potential role of new mini-TEE probes in adult patients with DMVR.