Towards a compact spherical tokamak fusion pilot plant

The question of size of a tokamak fusion reactor is central to current fusion research especially with the large device, ITER, under construction and even larger DEMO reactors under initial engineering design. In this paper, the question of size is addressed initially from a physics perspective. It is shown that in addition to size, field and plasma shape are important too, and shape can be a significant factor. For a spherical tokamak (ST), the elongated shape leads to significant reductions in major radius and/or field for comparable fusion performance. Further, it is shown that when the density limit is taken into account, the relationship between fusion power and fusion gain is almost independent of size, implying that relatively small, high performance reactors should be possible. In order to realize a small, high performance fusion module based on the ST, feasible solutions to several key technical challenges must be developed. These are identified and possible design solutions outlined. The results of the physics, technical and engineering studies are integrated using the Tokamak Energy system code, and the results of a scoping study are reviewed. The results indicate that a relatively small ST using high temperature superconductor magnets should be feasible and may provide an alternative, possibly faster, ‘small modular’ route to fusion power. This article is part of a discussion meeting issue ‘Fusion energy using tokamaks: can development be accelerated?’.

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On the size of tokamak fusion power plants

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2017.0437 ◽

2019 ◽

Vol 377 (2141) ◽

pp. 20170437 ◽

Cited By ~ 5

Author(s):

Hartmut Zohm

Keyword(s):

Power Plants ◽

New Technology ◽

Fusion Energy ◽

Plasma Parameters ◽

Fusion Power ◽

Figures Of Merit ◽

Superconducting Coils ◽

Critical Technology ◽

Alternative Approach ◽

Major Radius

Figures of merit for future tokamak fusion power plants (FPPs) are presented. It is argued that extrapolation from present-day experiments to proposed FPPs must follow a consistent development path, demonstrating the largest required leaps in intermediate devices to allow safe extrapolation to an FPP. This concerns both plasma physics and technology. At constant plasma parameters, the figures of merit depend on both major radius R and magnetic field B . We propose to use the term ‘size’ for a combination of R and B to avoid ambiguities in scaling arguments. Two routes to FPPs are discussed: the more conventional one increasing R , based on the assumption that B is limited by present technology; and an alternative approach assuming the availability of new technology for superconducting coils, allowing higher B . It is shown that the latter will lead to more compact devices, and, assuming a criterion based on divertor impurity concentration, is in addition more favourable concerning the exhaust problem. However, in order to obtain attractive steady-state tokamak FPPs, the required plasma parameters still require considerable progress with respect to present experiments. A credible strategy to arrive at these must hence be shown for both paths. In addition, the high-field path needs a demonstration of the critical technology items early on. This article is part of a discussion meeting issue ‘Fusion energy using tokamaks: can development be accelerated?’.

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Activation and transmutation of tungsten boride shields in a spherical tokamak

Nuclear Fusion ◽

10.1088/1741-4326/ac4866 ◽

2022 ◽

Author(s):

Colin Windsor ◽

Jack Astbury ◽

Guy Morgan ◽

Christopher L. Wilson ◽

Sam Humphry-Baker

Keyword(s):

High Temperature Superconductor ◽

Boron Content ◽

Fusion Reaction ◽

Gas Production ◽

Spherical Tokamak ◽

Fusion Power ◽

Helium Gas ◽

Shielding Properties ◽

Tungsten Borides ◽

Central High

Abstract The FISPACT-II code is used to compute the levels of activation and transmutation of tungsten borides for shielding the central High Temperature Superconductor (HTS) core of a spherical tokamak fusion power plant during operations at 200 MW fusion power for 30 years and after shutting down for 10 years. The materials considered were W2B, WB, W2B5 and WB4 along with a sintered borocarbide B0.329C0.074Cr0.024Fe0.274W0.299, monolithic W and WC. Calculations were made within shields composed of each material, for five reactor major radii from 1400 to 2200 mm, and for six 10B isotope concentrations and at five positions across the shield. The isotopic production and decay in each shield is detailed. The activation of boride materials is lower than for either W or WC and is lowest of all for W2B5. While isotopes from tungsten largely decay within 3 years of shut-down, those from boron have a much longer decay life. An acceptable 70% of the absorbing 10B isotope will remain after 30 years of operations behind the first wall for a 1400 mm radius tokamak. Gaseous production is problematic in boride shields, where 4He in particular is produced in quantities 3 orders of magnitude higher than in W or WC shields. The FISPACT-II displacements per atom (dpa) tend to increase with boron content, although they decrease with increased 10B isotopic content. The dpa ranges of boride shields tend to lie between those of W and WC. Overall, the results confirm that the favourable fusion reaction shielding properties of W2B5 are not seriously challenged by its irradiation and transmutation properties, although helium gas production could be a challenge to its thermal and mechanical properties.

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Political and commercial prospects for inertial fusion energy

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2020.0008 ◽

2020 ◽

Vol 378 (2184) ◽

pp. 20200008 ◽

Cited By ~ 2

Author(s):

Andrew Holland

Keyword(s):

Fusion Energy ◽

Energy System ◽

High Gain ◽

Inertial Fusion ◽

Inertial Fusion Energy ◽

Global Energy ◽

Fusion Power ◽

Energy Part ◽

System Today ◽

Global Energy System

Fusion energy holds the prospect of an energy source that is clean, safe, affordable and limitless. It will transform the global energy system. Today, around $1.5 billion in private capital has been invested in companies that are working on transformative approaches to fusion. Annually, even more than that is spent on fusion research by governments around the world. However, just achieving a scientific demonstration of fusion power will not be enough on its own to transition the global energy system. It will require innovations in the legal, regulatory, commercial and political spheres to support the massive deployment of fusion power that we know will be necessary to meet the global challenges of climate change and energy scarcity. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)'.

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The Mediating Role of Employee Engagement in the Relationship between High Performance Work Practices and Job Performance

SSRN Electronic Journal ◽

10.2139/ssrn.2694991 ◽

2015 ◽

Author(s):

Dr. Naval garg ◽

Brij Sharma

Keyword(s):

Job Performance ◽

Employee Engagement ◽

High Performance ◽

Work Practices ◽

Mediating Role ◽

High Performance Work Practices ◽

The Relationship

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Exergy Assessment and Thermo-Economic Analysis of Hybrid Solar Systems with Seasonal Storage and Heat Pump Coupling in the Social Housing Sector in Zaragoza

Energies ◽

10.3390/en14051279 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1279

Author(s):

Amaya Martínez-Gracia ◽

Sergio Usón ◽

Mª Teresa Pintanel ◽

Javier Uche ◽

Ángel A. Bayod-Rújula ◽

...

Keyword(s):

Heat Pump ◽

Social Housing ◽

Energy System ◽

Simulation Software ◽

Solar Panels ◽

Solar Systems ◽

Under Construction ◽

The Cost ◽

Solar Resource ◽

Solar Field

A real case study of an energy system based on a Solar Assisted Heat Pump (SAHP) fed by hybrid photovoltaic-thermal solar panels (PVT) and seasonal storage (SS) is presented in this paper. Exergy and exergy cost analyses are proposed as complementary methods for the assessment and better understanding of the efficiency of this cogeneration solar configuration. The system performance takes advantage of storage heat in summer, when the solar resource is high in Spain, and is then later consumed during the cold winter (heating season). The building is devoted to social housing, and it is currently under construction. The assessment is based on simulations developed using TRNSYS, a dynamic simulation software for energy systems. Results show that the unit exergy cost of the solar field is around 6. The cost of the seasonal storage is higher, about 13, and its formation is affected both by its own irreversibility and by the irreversibility of the PVT solar field. The cost of the heat delivered by the heat pump is around 15, being affected by all the upstream units and even by the grid. Besides, the analysis points out strategies for improving the system efficiency, such as increasing the size of the storage tank or improving the control strategy of the boiler.

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The Relationship between Learning Styles and Academic Performance: Consistency among Multiple Assessment Methods in Psychology and Education Students

Sustainability ◽

10.3390/su13063341 ◽

2021 ◽

Vol 13 (6) ◽

pp. 3341

Author(s):

Jesús Maya ◽

Juan F. Luesia ◽

Javier Pérez-Padilla

Keyword(s):

Early Childhood ◽

Academic Performance ◽

Learning Styles ◽

Primary Education ◽

High Performance ◽

Multiple Choice ◽

Assessment Methods ◽

Theory And Practice ◽

Education Students ◽

The Relationship

Universities strive to ensure quality education focused on the diversity of the student body. According to experiential learning theory, students display different learning preferences. This study has a three-fold objective: to compare learning styles based on personal and educational variables, to analyze the association between learning styles, the level of academic performance, and consistency of performance in four assessment methods, and to examine the influence of learning dimensions in students with medium-high performance in the assessment methods. An interdisciplinary approach was designed involving 289 psychology, early childhood education and primary education students at two universities in Spain. The Learning Style Inventory was used to assess learning styles and dimensions. The assessment methods used in the developmental psychology course included the following question formats: multiple-choice, short answer, creation-elaboration and an elaboration question on the relationship between theory and practice. Univariate analysis, multivariate analysis, and binomial logistic models were computed. The results reveal Psychology students to be more assimilative (theoretical and abstract), while early childhood and primary education students were evenly distributed among styles and were more divergent and convergent (practical) in absolute terms. In addition, high scores in perception (abstract conceptualization) were associated with a high level of performance on the multiple-choice tests and the elaboration question on the relationship between theory and practice. Abstract conceptualization was also associated with medium-high performance in all assessment methods and this variable predicted consistent high performance, independent of the assessment method. This study highlights the importance of promoting abstract conceptualization. Recommendations for enhancing this learning dimension are presented.

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Relationship between Plasma Trimethylamine N-Oxide Levels and Renal Dysfunction in Patients with Hypertension

Kidney & Blood Pressure Research ◽

10.1159/000513033 ◽

2021 ◽

pp. 1-12

Author(s):

Jia Zhou ◽

Dingkun Wang ◽

Bingong Li ◽

Xuelian Li ◽

Xingjun Lai ◽

...

Keyword(s):

Blood Pressure ◽

Kidney Disease ◽

Renal Dysfunction ◽

High Performance ◽

Characteristic Curve ◽

Area Under The Curve ◽

Hypertensive Patients ◽

Ckd Stage ◽

Liquid Chromatography Tandem Mass ◽

The Relationship

Introduction: Trimethylamine N-oxide (TMAO) is a metabolite produced by gut bacteria. Although increased TMAO levels have been linked to hypertension (HTN) and chronic kidney disease (CKD) with poor prognosis, no clinical studies have directly addressed the relationship between them. In this study, we investigated the relationship between TMAO and renal dysfunction in hypertensive patients. Methods: We included healthy controls (n = 50), hypertensive patients (n = 46), and hypertensive patients with renal dysfunction (n = 143). Their blood pressure values were taken as the highest measured blood pressure. Renal function was evaluated using the estimated glomerular filtration rate. Plasma TMAO levels were measured using high-performance liquid chromatography tandem mass spectrometry. Results: We found significant differences in plasma TMAO levels among the 3 groups (p < 0.01). The plasma TMAO of patients with HTN was significantly higher than that of healthy people, and the plasma TMAO of patients with HTN complicated by renal dysfunction was significantly higher than either of the other groups. Patients in the highest TMAO quartile were at a higher risk of developing CKD stage 5 than those in the lowest quartile. In the receiver operating characteristic curve, the area under the curve of TMAO combined with β 2-macroglobulin for predicting renal dysfunction in patients with HTN was 0.85 (95% confidence interval 0.80–0.90). Conclusion: An elevated TMAO level reflects higher levels of HTN and more severe renal dysfunction. TMAO, combined with β 2-macroglobulin levels, may assist in diagnosing CKD in hypertensive patients. Plasma TMAO has predictive value for early kidney disease in hypertensive patients.

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Changes in Optical Properties upon Dye–Clay Interaction: Experimental Evaluation and Applications

Nanomaterials ◽

10.3390/nano11010197 ◽

2021 ◽

Vol 11 (1) ◽

pp. 197

Author(s):

Giorgia Giovannini ◽

René M. Rossi ◽

Luciano F. Boesel

Keyword(s):

Optical Properties ◽

Hybrid Materials ◽

High Performance ◽

Fluorescent Properties ◽

Chemical Mechanisms ◽

Strong Electrostatic Interaction ◽

Potential Applications ◽

Photochemical Properties ◽

Physical And Chemical ◽

The Relationship

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

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Polyimide-Silica Hybrid Aerogels with High Mechanical Strength for Thermal Insulation Applications

MRS Proceedings ◽

10.1557/opl.2011.380 ◽

2011 ◽

Vol 1306 ◽

Cited By ~ 2

Author(s):

Wenting Dong ◽

Wendell Rhine ◽

Shannon White

Keyword(s):

Thermal Conductivity ◽

High Performance ◽

Ambient Conditions ◽

Separation Membranes ◽

Low Dielectric ◽

Aging Conditions ◽

Hybrid Aerogels ◽

Mechanical Strengths ◽

The Relationship ◽

Silica Hybrid

ABSTRACTHigh performance polyimides have been widely investigated as materials with excellent thermal, mechanical, and electronic properties due to their highly rigid structures. Aspen has developed an approach to prepare polyimide aerogels which have applications as low dielectric constant materials, separation membranes, catalyst supports and insulation materials. In this paper, we will discuss the preparation of polyimide-silica hybrid aerogel materials with good mechanical strengths and low thermal conductivities. The polyimide-silica hybrid aerogels were made by a two-step process and the materials were characterized to determine thermal conductivity and compressive strength. Results show that compressive moduli of the polyimide-silica hybrid aerogels increase dramatically with density (power law relationship). Thermal conductivity of the aerogels is dependent on the aging conditions and density, with the lowest value achieved so far being ~12 mW/m-K at ambient conditions. The relationship between aerogel density and surface area, thermal stability, porosity and morphology of the nanostructure of the polyimide-silica hybrid aerogels are also described in this paper.

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