During the pre-conceptual design phase of DEMO, different alternatives have been explored to be implemented as tritium extraction and removal system (TERS) for the blanket concepts considered in ...EUROfusion. The TERS is conceived to extract tritium from the breeder and to route it to the Tritium Plant for final processing. A careful review showed that those blankets operated with PbLi should use the permeation against vacuum (PAV) technique as primary option which is based on a one-step, fully continuous procedure. In this paper, a conceptual design of the TERS for the dual coolant lithium lead (DCLL) breeding blanket is presented, based on the European DEMO2015 layout (18 sectors, 2037 MW fusion power). The P&ID of the proposed TERS, integrated in the DCLL-PbLi loop, includes valves and instrumentation, as well as a revised design of the DCLL-PAV. The dimensioning of the permeator considered a tritium extraction efficiency of 80%. An exhaustive investigation on the vacuum system needed for the PAV is also presented. The choice of the most promising vacuum systems took into account the reliability and tritium compatibility of both high and rough pumps. Their pumping requirements, which are dependent on the PAV efficiency, tritium solubility and tritium partial pressure in the loop, are also discussed in this work.
In a fusion reactor based on liquid breeding blankets, tritium is generated due to the neutron irradiation of lithium based alloy, such as eutectic lead-lithium (PbLi). Then, tritium is extracted ...from the liquid metal by means of technologies that are presently under development such as the vacuum sieve tray, the permeation against vacuum or the gas liquid contactors. Nevertheless, for the experimental validation of these technologies at laboratory scale, hydrogen isotopes cannot be generated in situ in the liquid metal as in the breeding blanket. Hence, a system able to inject the gas in the flowing liquid at desired concentrations is required, avoiding the formation of bubbles as a consequence of the low solubility of hydrogen/deuterium in PbLi. The system should be capable of solubilizing the hydrogen to replicate as close as possible the conditions of a breeding blanket.
A design of an injector based on a permeable membrane is here presented, being the driving force the gradient of concentrations existing between the two surfaces of the membrane. A hydrogen transport model for a tube-in-tube injector has been developed, showing that the injected hydrogen flux is proportional to the tube radius. However, the change on this parameter, that affects the velocity of the liquid and thus the mass transport coefficient, has opposite consequences on the rate of injection whose final impact relays on the properties of the employed membrane.
An evaluation of the physical and geometrical aspects of a conceptual injector is depicted with the aim of optimizing the design to obtain adequate injection rate depending on the facility where the injector is installed. Finally, a conceptual design of a system to be implemented in an experimental PbLi loop for the validation of the permeation against vacuum technique for tritium extraction from PbLi is presented. The injector is based on a multi-tube component made of niobium able to inject hydrogen at the same rate as it is extracted under relevant conditions for a Dual Coolant Lithium Lead breeding blanket.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Awake prone positioning (APP) has been advocated to improve oxygenation and prevent intubation of patients with acute hypoxemic respiratory failure due to coronavirus disease 2019 (COVID-19). This ...paper aims to synthesize the available evidence on the efficacy of APP.
We performed a systematic review of proportional outcomes from observational studies to compare intubation rate in patients treated with APP or with standard care.
A total of 46 published and 4 unpublished observational studies that included 2,994 subjects were included, of which 921 were managed with APP and 870 were managed with usual care. APP was associated with significant improvement of oxygenation parameters in 381 cases of 19 studies that reported this outcome. Among the 41 studies assessing intubation rates (870 subjects treated with APP and 852 subjects treated with usual care), the intubation rate was 27% (95% CI 19-37%) as compared to 30% (95% CI 20-42%) (
= .71), even when duration of application, use of adjunctive respiratory assist device (high-flow nasal cannula or noninvasive ventilation), and severity of oxygenation deficit were taken into account. There appeared to be a trend toward improved mortality when APP was compared with usual care (11% vs 22%), which was not statistically significant.
APP was associated with improvement of oxygenation but did not reduce the intubation rate in subjects with acute respiratory failure due to COVID-19. This finding is limited by the high heterogeneity and the observational nature of included studies. Randomized controlled clinical studies are needed to definitively assess whether APP could improve key outcome such as intubation rate and mortality in these patients.
•A conceptual design of a Permeator Against Vacuum is presented.•The efficiency is dependent on geometry and Tritium transport.•The use of different membrane materials is discussed.•A squared PAV ...with alternated PbLi flowing and vacuum flat ducts is designed.•80% efficiency of Tritium extraction is accomplished under DCLL-BB requirements.
One of the most important issues in future fusion power plants is the extraction of tritium generated in the breeders in order to achieve self-sufficiency. When the breeder is a liquid metal one of the most promising techniques is the Permeation Against Vacuum, whose principle is based on tritium diffusion through a permeable membrane in contact with the liquid metal carrier and its further extraction by a vacuum pump. A conceptual design of permeator has been developed, taking into account the features of a DEMO reactor with a Dual Coolant Lithium Lead (DCLL) breeder blanket. The study is based on the analysis of different membranes and geometries aiming at the overall efficiency (extraction capability) of the device, as well as its compatibility with the breeder material. The permeator is based on a rectangular section multi-channel distribution where the liquid metal channels and vacuum channels are alternated in order to maximize the contact area and therefore to promote tritium transport from the bulk to the walls. The resulting permeator design has an excellent estimated extraction efficiency, of 80%, in a relatively compact device.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•The most relevant aspects of the design of the European DCLL MMS design adapted to DEMO 2017 are described.•Several channels configurations have been assessed in order to select the most adequate ...for the whole FW.•Specific models have been created to study the impact of the change to DEMO 2017 on thermal-hydraulics at module level.•The presence of important heat flux peaks on the FW is translated into a poorer performance of the whole blanket.•The overall TBR has been kept in a significant value of 1.173. The main shielding responses are fulfilled.
The capability of the breeding blanket to efficiently fulfill its main requirements: tritium breeding, power extraction and neutron shielding is strongly sensitive on the variation of the geometrical constraints imposed by plasma physics and the integration with the rest of the plant systems. Within the Power Plant Physics and Technology Programme, EUROfusion is developing a Dual-Coolant Lithium-Lead (DCLL) breeding blanket based on the multi-module segment approach. In the current DEMO reactor specification released in 2017, the outboard blanket thickness has been decreased with the aim of providing better stability to the plasma and increasing its elongation. Besides, the first wall has been shaped in order to optimize the heat flux loads from the plasma. This work describes the main aspects of the adaptation of the EU DCLL breeding blanket to the characteristics of DEMO 2017 and assesses the influence of the changes on its thermal-hydraulic and neutronic performances.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The manufacturing design of a Permeator Against Vacuum prototype is presented.•The PAV will be implemented in a PbLi loop to demonstrate the technique.•Operational inputs (mass flow, temperature) ...are evaluated for a fixed geometry.•Two approaches are compared in terms of efficiency, assembly and endurance.•A PAV based on vanadium membranes and steel supporting structure is proposed.
Tritium recovery is one of the major issues of a future DEMO reactor, in order to comply with the requirements of tritium self-sufficiency. Within the EUROfusion Programme the permeation against vacuum (PAV) technique has been considered as baseline for those blankets which use PbLi as breeder.
A conceptual design of a rectangular multi-channel PAV for its implementation in an experimental PbLi loop, under construction at CIEMAT, has been produced. A comparison between vanadium/niobium/tantalum and α-Fe membranes has been performed in terms of costs, machining, mechanical resistance and efficiency resulting in a design based on vanadium membranes and a stainless steel structure.
Structural calculations are also presented, paying special attention to the interface between the membranes and the main structure in order to avoid leakages. Other important aspects such as keeping an adequate vacuum level have also been considered.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Two clamping concepts have been proposed, including a RH device to install them.•Plastic strain due to thermal stresses during cooling is small.•The capillary flow model shows a fairly good ...agreement with the analytical model.•The tritium permeation phenomenon is not relevant for this selection of materials.•The brazed joints strength could be enough to suppress the external clamp.
The main unavailability sources in a fusion power plant will be caused by the replacement of large in-vessel components, as well as by components failure and short duration maintenance tasks and inspection processes. The development and validation of remotely operable leak-free pipe connectors for helium, water and liquid metal is a key issue for faster and more reliable replacement of in-vessel components. In this work, some advances in the design of a connector by brazing for DEMO blanket pipes are presented. A new clamping concept to stiffen the connector is proposed, although different previous works suggest the mechanical strength of the brazed joint could be enough and the clamp may not be necessary. A characterization of the mechanical behavior of the brazed joint, a CFD approach for modeling the capillary flow of the BAu-4 filler metal during the brazing process and a preliminary assessment on the issue of tritium permeation are included.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Presentamos un estudio arqueoastronómico de dos santuarios rupestres situados en abrigos rocosos, Cueva del Rey Moro y Cueva Negra. Cueva del Rey Moro es un santuario ibérico asociado al poblado de ...Castellar de Meca. Aunque descartamos resultados anteriores que proponían la orientación del núcleo del santuario hacia el ocaso del solsticio de verano, encontramos dos posibles marcadores de ocaso solar en el día mitad entre solsticios (fecha cercana al equinoccio) y en el solsticio de verano en sendos cerros del horizonte occidental. Cueva Negra fue un importante lugar de culto en época romana como atestiguan los tituli picti encontrados en su interior, aunque también se evidencia su uso cultual durante época ibérica. Nuestro estudio indica la existencia de un marcador muy preciso del día mitad entre solsticios sobre la ladera de la Sierra de Abanilla, aunque sin duda, el resultado más interesante es que el orto solar sobre la cumbre puntiaguda de dicha sierra, el pico Zulum, se produce, en la actualidad, el 27 de marzo, justamente la fecha del calendario juliano que se recoge en varias inscripciones de los tituli picti, y que podría corresponder con la festividad de la lavatio de la Magna Mater. Este espectacular orto pudo haberse utilizado como marcador de la fecha de la celebración principal del santuario romano si las inscripciones (al menos aquellas que muestran dicha fecha) hubieran sido realizadas durante el siglo III d.C., pues en ese siglo las fechas de los calendarios juliano y gregoriano actual coincidieron. Este resultado es consistente con los valores bajos de la horquilla de datación paleográfica propuesta para las inscripciones.
The Water Cooled Lithium Lead (WCLL) blanket is one of the four breeder blanket technologies under consideration within the framework of the EUROfusion Consortium activities. The aim of this work is ...to develop a preliminary model that can track tritium concentration and tritium fluxes along each part of the WCLL blanket and its ancillary systems at any time.
Because of tritium's nature, the phenomena of diffusion, dissociation, recombination and solubilization have been taken into account when describing the tritium behavior inside the lead-lithium channels, the structural materials and the water coolant circuits. The simulations have been performed using the object oriented modeling software EcosimPro.
Results have been obtained for the pulsed generation scenario of the European demonstration power plant (DEMO). The tritium inventory in every part of the blanket has been computed. Permeation rates have been calculated as well allowing to know how much tritium ends up in the coolant system and how much remains in the liquid metal. The amount of tritium extracted from the lead-lithium loop has been also obtained. All this information allows having a global perspective of tritium behavior all over the blanket at any time.
The model provides valuable information for the design of the WCLL blanket. More complex upgrades are planned to be implemented based on this model in future stages of the EUROfusion project.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
PDF
