| 1. |
- Tran, Chi Thanh, 1965-
(author)
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The Effective Convectivity Model for Simulation and Analysis of Melt Pool Heat Transfer in a Light Water Reactor Pressure Vessel Lower Head
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Severe accidents in a Light Water Reactor (LWR) have been a subject of intense research for the last three decades. The research in this area aims to reach understanding of the inherent physical phenomena and reduce the uncertainties in their quantification, with the ultimate goal of developing models that can be applied to safety analysis of nuclear reactors, and to evaluation of the proposed accident management schemes for mitigating the consequences of severe accidents. In a hypothetical severe accident there is likelihood that the core materials will be relocated to the lower plenum and form a decay-heated debris bed (debris cake) or a melt pool. Interactions of core debris or melt with the reactor structures depend to a large extent on the debris bed or melt pool thermal hydraulics. In case of inadequate cooling, the excessive heat would drive the structures' overheating and ablation, and hence govern the vessel failure mode and timing. In turn, threats to containment integrity associated with potential ex-vessel steam explosions and ex-vessel debris uncoolability depend on the composition, superheat, and amount of molten corium available for discharge upon the vessel failure. That is why predictions of transient melt pool heat transfer in the reactor lower head, subsequent vessel failure modes and melt characteristics upon the discharge are of paramount importance for plant safety assessment. The main purpose of the present study is to develop a method for reliable prediction of melt pool thermal hydraulics, namely to establish a computational platform for cost-effective, sufficiently-accurate numerical simulations and analyses of core Melt-Structure-Water Interactions in the LWR lower head during a postulated severe core-melting accident. To achieve the goal, an approach to efficient use of Computational Fluid Dynamics (CFD) has been proposed to guide and support the development of models suitable for accident analysis. The CFD method, on the one hand, is indispensable for scrutinizing flow physics, on the other hand, the validated CFD method can be used to generate necessary data for validation of the accident analysis models. Given the insights gained from the CFD study, physics-based models and computationally-efficient tools are developed for multi-dimensional simulations of transient thermal-hydraulic phenomena in the lower plenum of a LWR during the late phase of an in-vessel core melt progression. To describe natural convection heat transfer in an internally heated volume, and molten metal layer heated from below and cooled from the top (and side) walls, the Effective Convectivity Models (ECM) are developed and implemented in a commercial CFD code. The ECM uses directional heat transfer characteristic velocities to transport the heat to cooled boundaries. The heat transport and interactions are represented through an energy-conservation formulation. The ECM then enables 3D heat transfer simulations of a homogeneous (and stratified) melt pool formed in the LWR lower head. In order to describe phase-change heat transfer associated with core debris or binary mixture (e.g. in a molten metal layer), a temperature-based enthalpy formulation is employed in the Phase-change ECM (so called the PECM). The PECM is capable to represent natural convection heat transfer in a mushy zone. Simple formulation of the PECM method allows implementing different models of mushy zone heat transfer for non-eutectic mixtures. For a non-eutectic binary mixture, compositional convection associated with concentration gradients can be taken into account. The developed models are validated against both existing experimental data and the CFD-generated data. ECM and PECM simulations show a superior computational efficiency compared to the CFD simulation method. The ECM and PECM methods are applied to predict thermal loads imposed on the vessel wall and Control Rod Guide Tubes (CRGTs) during core debris heatup and melting in a Boiling Water Reactor (BWR) lower plenum. It is found that during the accident progression, the CRGT cooling plays a very important role in reducing the thermal loads on the reactor vessel wall. Results of the ECM and PECM simulations suggest a high potential of the CRGT cooling to be an effective measure for severe accident management in BWRs.
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| 2. |
- Fuller, Robert, et al.
(author)
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Lessons from the greenest city
- 2013
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In: Proceedings of the 2013 Urban Design Conference. - Nerang, Qld. Australia. ; , s. 54-61
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Conference paper (peer-reviewed)abstract
- In 2007, the City of Växjö in Sweden was voted the greenest city in Europe. Over an 18-year period, greenhouse gas emissions per resident have been reduced by 41%. How has Växjö achieved this impressive result and are there any lessons that could be transferred to Australian cities? This paper describes research which compares Växjö with the Victorian City of Ballarat. The research shows that per capita emissions for Ballarat are 133% higher than those in Växjö. Upgrading the typical Ballarat home to a 6-star rating, and installing a gas-boosted solar water heater and 4.0 kW PV system on the roof could reduce per capita emissions to similar levels to those in Växjö.
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| 3. |
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| 4. |
- Vorona, Igor, et al.
(author)
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Identification of Ga interstitials in GaAlNP
- 2003
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In: Proceedings of the 22nd International Conference on Defects in Semiconductors. - : Elsevier BV. ; , s. 466-469
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Conference paper (peer-reviewed)abstract
- New dilute nitride Ga1-xAlxNyP1-y alloys grown by gas-source molecular beam epitaxy have been studied by the optical detected magnetic resonance technique. Two paramagnetic defect centers with an effective electron spin S = 1/2 were observed and shown to involve Ga interstitials (denoted as Gai-A and Gai-B), both exhibiting the characteristic hyperfine (HF) structure from the two Ga isotopes. The HF interaction is shown to be nearly isotropic and rather strong, providing evidence for an A1 symmetry of the electron wave function highly localized at the Ga atom. We tentatively attribute Gai-A and Gai-B to the interstitial sites surrounded by group-III and group-(V and III) atoms, respectively. © 2003 Elsevier B.V. All rights reserved.
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| 5. |
- Wang, Guo-Dong, et al.
(author)
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Out of southern East Asia : the natural history of domestic dogs across the world
- 2016
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In: Cell Research. - : Nature Publishing Group. - 1001-0602 .- 1748-7838. ; 26:1, s. 21-33
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Journal article (peer-reviewed)abstract
- The origin and evolution of the domestic dog remains a controversial question for the scientific community, with basic aspects such as the place and date of origin, and the number of times dogs were domesticated, open to dispute. Using whole genome sequences from a total of 58 canids (12 gray wolves, 27 primitive dogs from Asia and Africa, and a collection of 19 diverse breeds from across the world), we find that dogs from southern East Asia have significantly higher genetic diversity compared to other populations, and are the most basal group relating to gray wolves, indicating an ancient origin of domestic dogs in southern East Asia 33 000 years ago. Around 15 000 years ago, a subset of ancestral dogs started migrating to the Middle East, Africa and Europe, arriving in Europe at about 10 000 years ago. One of the out of Asia lineages also migrated back to the east, creating a series of admixed populations with the endemic Asian lineages in northern China before migrating to the New World. For the first time, our study unravels an extraordinary journey that the domestic dog has traveled on earth.
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| 6. |
- Alvarez de Davila, Eliana, et al.
(author)
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Vilket stöd behöver företag och organisationer inom kemikalieområdet? En förstudie. What support do companies and organisations need regarding chemicals. A pilot study
- 2002
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Reports (other academic/artistic)abstract
- När det gäller användning av kemikalier finns det många olika lagar och regler som ska följas av de företag som hanterar kemikalier. Tillsynen sköts av flera myndigheter. Intervjuer har gjorts med företrädare för berörda myndigheter, för arbetsmarknadens parter, för tre mindre företag och organisationer som på olika sätt arbetar med frågor om kemikalier och arbetsmiljö. Studien visar att det finns behov av förbättringar på flera olika områden bl a * förbättrad samordning mellan de ansvariga myndigheterna Arbetsmiljöverket, Räddningsverket, Naturvårdsverket och Kemikalieinspektionen * förbättrad kontroll av varuinformationsblad (säkerhetsdatablad) * mer av handfasta arbetsmaterial som hjälper speciellt mindre företag att leva upp till gällande regler. Detta anges som ett högprioriterat område * ett tydligare nätverk av experter inom kemikalieområdet, som kan bistå med expertkunnande till bl a arbetsmarknadens parter och till företag *flera av de insatser som behövs, skulle kunna samordnas via en arbetsmiljöportal
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| 7. |
- Gajdoš, Matúš, et al.
(author)
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Chiral Alcohols from Alkenes and Water: Directed Evolution of a Styrene Hydratase
- 2023
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In: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:7
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Journal article (peer-reviewed)abstract
- Enantioselective synthesis of chiral alcohols through asymmetric addition of water across an unactivated alkene is a highly sought-after transformation and a big challenge in catalysis. Herein we report the identification and directed evolution of a fatty acid hydratase from Marinitoga hydrogenitolerans for the highly enantioselective hydration of styrenes to yield chiral 1-arylethanols. While directed evolution for styrene hydration was performed in the presence of heptanoic acid to mimic fatty acid binding, the engineered enzyme displayed remarkable asymmetric styrene hydration activity in the absence of the small molecule activator. The evolved styrene hydratase provided access to chiral alcohols from simple alkenes and water with high enantioselectivity (>99 : 1 e.r.) and could be applied on a preparative scale.
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| 8. |
- Kobyakov, D. N., et al.
(author)
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Superfluid Liquid Crystals : Pasta Phases in Neutron Star Crusts
- 2018
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In: Journal of Experimental and Theoretical Physics. - : PLEIADES PUBLISHING INC. - 1063-7761 .- 1090-6509. ; 127:5, s. 851-859
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Journal article (peer-reviewed)abstract
- The pasta phases predicted to occur near the inner boundary of the crust of a neutron star resemble liquid crystals, a smectic A in the case of sheet-like nuclei (lasagna) and the columnar phase in the case of rod-like nuclei (spaghetti). An important difference compared with usual liquid crystals is that the nucleons are superfluid. We develop the hydrodynamic equations for this system and use them to study collective oscillations. Nucleon superfluidity leads to important qualitative differences in the spectra of these oscillations and also increases their frequencies compared with ordinary liquid crystals. We discuss a number of directions for future work.
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