scholarly journals Modelling of dust generation, transport and remobilization in full-metal fusion reactors

Author(s):  
Svetlana Ratynskaia ◽  
Ladislas Vignitchouk ◽  
Panagiotis Tolias

Abstract The design, licensing and operation of magnetic confinement fusion reactors impose various limitations on the amount of metallic dust particles residing inside the plasma chamber. In this context, predictive studies of dust production and migration constitute one of the main sources of relevant data. These are mainly conducted using dust transport codes, which rely on coupled dust-plasma and dust-wall interaction models, and require external input on the dust and droplet initial conditions. Some particularities of dust modelling in reactor-relevant conditions are analyzed with an emphasis on dust generation mechanisms relevant for disruption scenarios and on dust remobilization mechanisms relevant for ramp-up scenarios. Emerging topics such as dust production by runaway electron impact and pre-plasma remobilization of magnetic dust are also discussed.

1996 ◽  
Vol 30 (1) ◽  
pp. 79-87 ◽  
Author(s):  
F. J. Potgieter ◽  
P. I. Wilke

Vermiculite, pine shavings and unbleached eucalyptus pulp contact bedding were compared for dust content, dust production (as a result of animal activity), moisture absorption properties and ammonia production. The percentage of dust particles <300 µm found in pine shavings and vermiculite was 18 and 8 times greater respectively than was found in eucalyptus pulp. The lowest ammonia levels (<1-1 ppm), measured on day 7, were obtained using eucalyptus pulp. Although the ammonia levels obtained for vermiculite compared very well with those of pulp, high levels of dust, up to 5 times more than pulp, were experienced with vermiculite. Pine shavings were associated with the highest ammonia concentration (1-3 ppm), but produced approximately 50% less dust than vermiculite. The water absorption properties obtained for pulp were between 35% and 76% higher than those obtained for vermiculite and pine shavings respectively.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Mendes ◽  
J. C. B. da Silva ◽  
J. M. Magalhaes ◽  
B. St-Denis ◽  
D. Bourgault ◽  
...  

AbstractInternal waves (IWs) in the ocean span across a wide range of time and spatial scales and are now acknowledged as important sources of turbulence and mixing, with the largest observations having 200 m in amplitude and vertical velocities close to 0.5 m s−1. Their origin is mostly tidal, but an increasing number of non-tidal generation mechanisms have also been observed. For instance, river plumes provide horizontally propagating density fronts, which were observed to generate IWs when transitioning from supercritical to subcritical flow. In this study, satellite imagery and autonomous underwater measurements are combined with numerical modeling to investigate IW generation from an initial subcritical density front originating at the Douro River plume (western Iberian coast). These unprecedented results may have important implications in near-shore dynamics since that suggest that rivers of moderate flow may play an important role in IW generation between fresh riverine and coastal waters.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
György Varga ◽  
Pavla Dagsson-Walhauserová ◽  
Fruzsina Gresina ◽  
Agusta Helgadottir

AbstractMineral dust emissions from Saharan sources have an impact on the atmospheric environment and sedimentary units in distant regions. Here, we present the first systematic observations of long-range Saharan dust transport towards Iceland. Fifteen Saharan dust episodes were identified to have occurred between 2008 and 2020 based on aerosol optical depth data, backward trajectories and numerical models. Icelandic samples from the local dust sources were compared with deposited dust from two severe Saharan dust events in terms of their granulometric and mineralogical characteristics. The episodes were associated with enhanced meridional atmospheric flow patterns driven by unusual meandering jets. Strong winds were able to carry large Saharan quartz particles (> 100 µm) towards Iceland. Our results confirm the atmospheric pathways of Saharan dust towards the Arctic, and identify new northward meridional long-ranged transport of giant dust particles from the Sahara, including the first evidence of their deposition in Iceland as previously predicted by models.


Author(s):  
M. E. Ricotti ◽  
F. Bianchi ◽  
L. Burgazzi ◽  
F. D’Auria ◽  
G. Galassi

The strategy of approach to the problem moves from the consideration that a passive system should be theoretically more reliable than an active one. In fact it does not need any external input or energy to operate and it relies only upon natural physical laws (e.g. gravity, natural circulation, internally stored energy, etc.) and/or “intelligent” use of the energy inherently available in the system (e.g. chemical reaction, decay heat, etc.). Nevertheless the passive system may fail its mission not only as a consequence of classical mechanical failure of components, but also for deviation from the expected behaviour, due to physical phenomena mainly related to thermalhydraulics or due to different boundary and initial conditions. The main sources of physical failure are identified and a probability of occurrence is assigned. The reliability analysis is performed on a passive system which operates in two-phase, natural circulation. The selected system is a loop including a heat source and a heat sink where the condensation occurs. The system behavior under different configurations has been simulated via best-estimate code (Relap5 mod3.2). The results are shown and can be treated in such a way to give qualitative and quantitative information on the system reliability. Main routes of development of the methodology are also depicted.


2016 ◽  
Author(s):  
Mohamed Abdelkader ◽  
Swen Metzger ◽  
Benedikt Steil ◽  
Klaus Klingmüller ◽  
Holger Tost ◽  
...  

Abstract. Transatlantic dust transport has many implications for the atmosphere, ocean and climate. We present a modeling study on the impact of the key processes (dust emissions flux, convection and dust aging parameterizations) that control the transatlantic dust transport. Typically, the Inter-Tropical Convergence Zone (ITCZ) acts as a barrier for the meridional dust transport. To characterize the dust outflow over the Atlantic Ocean, we address two regional phenomena: (i) dust interactions with the ITCZ (DIZ) and (ii) the adjacent dust transport over the Atlantic Ocean (DTA). In the DTA zone, the dust loading shows a steep and linear gradient westward over the Atlantic Ocean where particle sedimentation is the dominant removal process, whereas in the DIZ zone cloud interactions and wet deposition predominate. To study the different impacts of aging, we present two case studies that exclude condensation and coagulation, and include dust aging at various levels of complexity. For dust aging, we consider the uptake of inorganic acids on the surface of mineral particles that form salt compounds. Calcium, used as a proxy for the overall chemically reactive dust fraction, drives the dust-related neutralization reactions leading to higher dust aerosol optical depth (AOD). The aged dust particles are transferred to the soluble aerosol modes in the model and are mixed with other species that originate from anthropogenic and natural sources. The neutralization products (salts) take up water vapor from the atmosphere and increase the dust AOD under subsaturated conditions. We define the "direct effect of dust aging" to refer to the increase in AOD as a result of hygroscopic growth. On the other hand, the aged dust is more efficiently removed (wet and dry) because of the increase in particle size and hygroscopicity. This more efficient removal reduces the dust AOD over the DIZ zone. We define this as the "indirect effect of dust aging", complementary to the direct effect that is dominant in the DTA zone. Distinction of the two aging effects helps develop insight into the regional importance of dust–air-pollution interactions.


2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Ligang Xu ◽  
Hailin Niu ◽  
Jin Xu ◽  
Xiaolong Wang

Protecting water resources from nitrate-nitrogen (NO3-N) contamination is an important public health concern and a major national environmental issue in China. Loss of NO3-N in soils due to leaching is not only one of the most important problems in agriculture farming, but is also the main factor causing nitrogen pollution in aquatic environments. Three typical intensive agriculture farmlands in Jiangyin City in China are selected as a case study for NO3-N leaching and modeling in the soil profile. In this study, the transport and fate of NO3-N within the soil profile and nitrate leaching to drains were analyzed by comparing field data with the simulation results of the LEACHM model. Comparisons between measured and simulated data indicated that the NO3-N concentrations in the soil and nitrate leaching to drains are controlled by the fertilizer practice, the initial conditions and the rainfall depth and distribution. Moreover, the study reveals that the LEACHM model gives a fair description of the NO3-N dynamics in the soil and subsurface drainage at the field scale. It can also be concluded that the model after calibration is a useful tool to optimize as a function of the combination “climate-crop-soil-bottom boundary condition” the nitrogen application strategy resulting for the environment in an acceptable level of nitrate leaching. The findings in this paper help to demonstrate the distribution and migration of nitrogen in intensive agriculture farmlands, as well as to explore the mechanism of groundwater contamination resulting from agricultural activities.


2008 ◽  
Vol 8 (3) ◽  
pp. 11967-11996 ◽  
Author(s):  
C. Mitsakou ◽  
G. Kallos ◽  
N. Papantoniou ◽  
C. Spyrou ◽  
S. Solomos ◽  
...  

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.


10.14311/1759 ◽  
2013 ◽  
Vol 53 (2) ◽  
Author(s):  
Vadym A. Makhlaj ◽  
Igor E. Garkusha ◽  
Nikolay N. Aksenov ◽  
Alexander A. Chuvilo ◽  
Igor S. Landman

Dust generation under powerful plasma stream impacts has been studied in ITER ELM simulation experiments with QSPA Kh-50 plasma accelerator. Repetitive plasma exposures of tungsten have been performed by 0.25 ms plasma pulses and the heat load varied in the range (0.1÷1.1) MJm-2. Main characteristics of dust particles such as a number of ejected particles, their velocity, angular distribution and start time from the surface are investigated. Dust particles have not been observed under heat load below the cracking threshold. Quantity of dust particles rises with increasing heat load. Average velocities of dust particles are found to be strongly dependent on their start time from the surface after beginning of plasma-surface interaction. Maximal velocity achieved a few tens of meters per second.


2020 ◽  
Author(s):  
Claire Ryder ◽  
Eleanor Highwood ◽  
Adrian Walser ◽  
Petra Walser ◽  
Anne Philipp ◽  
...  

&lt;p&gt;Mineral dust is an important component of the climate system, interacting with radiation, clouds, and biogeochemical systems and impacting atmospheric circulation, air quality, aviation, and solar energy generation. These impacts are sensitive to dust particle size distribution (PSD), yet models struggle or even fail to represent coarse (diameter (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;&lt;/span&gt;)&amp;#160;&lt;span&gt;&gt;2.5&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) and giant (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;&gt;20&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) dust particles and the evolution of the PSD with transport. Here we examine three state-of-the-art airborne observational datasets, all of which measured the full size range of dust (&lt;span&gt;&lt;em&gt;d&lt;/em&gt;=0.1&lt;/span&gt;&amp;#160;to&amp;#160;&lt;span&gt;&gt;100&lt;/span&gt;&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m) at different stages during transport with consistent instrumentation. We quantify the presence and evolution of coarse and giant particles and their contribution to optical properties using airborne observations over the Sahara (from the Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical eastern Atlantic (from the AER-D field campaign).&lt;/p&gt;&lt;p&gt;Observations show significantly more abundant coarse and giant dust particles over the Sahara compared to the SAL: effective diameters of up to 20&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m were observed over the Sahara compared to 4&amp;#8201;&lt;span&gt;&amp;#181;&lt;/span&gt;m in the SAL. Excluding giant particles over the Sahara results in significant underestimation of mass concentration (40&amp;#8201;%), as well as underestimates of both shortwave and longwave extinction (18&amp;#8201;% and 26&amp;#8201;%, respectively, from scattering calculations), while the effects in the SAL are smaller but non-negligible. The larger impact on longwave extinction compared to shortwave implies a bias towards a radiative cooling effect in dust models, which typically exclude giant particles and underestimate coarse-mode concentrations.&lt;/p&gt;&lt;p&gt;A compilation of the new and published effective diameters against dust age since uplift time suggests that two regimes of dust transport exist. During the initial 1.5&amp;#8201;d, both coarse and giant particles are rapidly deposited. During the subsequent 1.5 to 10&amp;#8201;d, PSD barely changes with transport, and the coarse mode is retained to a much greater degree than expected from estimates of gravitational sedimentation alone. The reasons for this are unclear and warrant further investigation in order to improve dust transport schemes and the associated radiative effects of coarse and giant particles in models.&lt;/p&gt;&lt;p&gt;This work has been recently published in ACP (Ryder, C. L., Highwood, E. J., Walser, A., Seibert, P., Philipp, A., and Weinzierl, B.: Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara, Atmos. Chem. Phys., 19, 15353&amp;#8211;15376, https://doi.org/10.5194/acp-19-15353-2019, 2019).&lt;/p&gt;


2020 ◽  
Vol 237 ◽  
pp. 02020
Author(s):  
Hossein Panahifar ◽  
Ruhollah Moradhaseli ◽  
Hadi Bourzoie ◽  
Mahdi Gholami ◽  
Hamid Reza Khalesifard

Optical properties of long-range Saharan dust particles transported to the Iran Plateau have been investigated. The results were derived from the measurements of a dual-wavelength Depolarized backscatter/Raman lidar and a Cimel CE318-2 sunphotometer. Observations were performed in Zanjan, Northwest Iran. The backward trajectory analysis show that the lofted dust plumes come from the Saharan desert and travel along Mediterranean Sea and Turkey toward Iran. The lidar ratio within the lofted dust layer has been found with mean values of 50 sr at 532 nm. For the depolarization ratio, mean values of 25% have been found.


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