| 1. |
- Horne, Gregory P., et al.
(author)
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DEHBA (di-2-ethylhexylbutyramide) gamma radiolysis under spent nuclear fuel solvent extraction process conditions
- 2020
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In: Radiation Physics and Chemistry. - : Elsevier. - 0969-806X .- 1879-0895. ; 170
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Journal article (peer-reviewed)abstract
- Di-2-ethylhexylbutyramide (DEHBA) has been proposed as part of a hydro-reprocessing solvent extraction system for the co-extraction of uranium and plutonium from spent nuclear fuel. However, there remains a lack of quantitative understanding of the impact of chemical environment on the radiation chemistry of DEHBA, especially under conditions expected in real-world solvent extraction processes. Therefore, we have undertaken a systematic investigation into the radiolytic degradation of DEHBA in n-dodecane under fully aerated and biphasic conditions. DEHBA integrity and degradation product formation were measured for both extraction (in contact with 4.0 M HNO3(aq)) and stripping (in contact with 0.1 M HNO3(aq)) formulations. At the lower acidity the rate of DEHBA/n-dodecane degradation was slow (G = -0.26 +/- 0.02 mu M J(-1)) whereas at the higher acidity this degradation was about 35% faster (G= -0.35 +/- 0.02 mu M J(-1)). Both values were much less than analogous measurements under deaerated conditions. Under continuously aerated conditions, FTIR and ESI-MS measurements identified the two major degradation products, bis-2-ethylhexylamine (b2EHA) and N-(2-ethylhexyl)butyramide (MEHBA), as well as the presence of additional oxidized product species. Solvent system performance was also investigated using uranium extraction and strip distribution ratio measurements. These studies showed that there was only minimal change in uranium extraction and stripping performance with absorbed gamma dose.
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| 2. |
- Horne, Gregory P., et al.
(author)
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Effect of chemical environment on the radiation chemistry of N,N-di-(2-ethylhexyl)butyramide (DEHBA) and plutonium retention
- 2019
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In: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 48:38, s. 14450-14460
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Journal article (peer-reviewed)abstract
- N,N-di-(2-ethylhexyl)butyramide (DEHBA) has been proposed as part of a hydro-reprocessing solvent extraction system for the co-extraction of uranium and plutonium from spent nuclear fuel, owing to its selectivity for hexavalent uranium and tetravalent plutonium. However, there is a critical lack of quantitative understanding regarding the impact of chemical environment on the radiation chemistry of DEHBA, and how this would affect process performance. Here we present a systematic investigation into the radiolytic degradation of DEHBA in a range of n-dodecane solvent system formulations, where we subject DEHBA to gamma irradiation, measure reaction kinetics, ligand integrity, degradation product formation, and investigate solvent system performance through uranium and plutonium extraction and strip distribution ratios. The rate of DEHBA degradation in n-dodecane was found to be slow (G = -0.31 +/- 0.02 mu mol J(-1)) but enhanced upon contact with the oxidizing conditions of the investigated solvent systems (organic-only, or in contact with either 0.1 or 3.0 M aqueous nitric acid). Two major degradation products were identified in the organic phase, bis-2-ethylhexylamine (b2EHA) and N-(2-ethylhexyl)butyramide (MEHBA), resulting from the cleavage of C-N bonds, and could account for the total loss of DEHBA up to similar to 300 kGy for organic-only conditions. Both b2EHA and MEHBA were also found to be susceptible to radiolytic degradation, having G-values of -0.12 +/- 0.01 and -0.08 +/- 0.01 mu mol J(-1), respectively. Solvent extraction studies showed: (i) negligible change in uranium extraction and stripping with increasing absorbed dose; and (ii) plutonium extraction and retention exhibits complex dependencies on absorbed dose and chemical environment. Organic-only conditions afforded enhanced plutonium extraction and retention attributed to b2EHA, while acid contacts inhibited this effect and promoted significant plutonium retention for the highest acidity. Overall it has been demonstrated that chemical environment during irradiation has a significant influence on the extent of DEHBA degradation and plutonium retention.
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| 3. |
- Häll, Carl Henrik, 1978-, et al.
(author)
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Adjustments of public transit operations planning process for the use of electric buses
- 2019
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In: Journal of Intelligent Transportation Systems / Taylor & Francis. - : Taylor & Francis. - 1547-2450 .- 1547-2442. ; 23:3, s. 216-230
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Journal article (peer-reviewed)abstract
- This work investigates and discusses how the introduction of electric buses (EB), both battery and plug-in hybrid EB, will and should change the operations planning of a public transit system. It is shown that some changes are required in the design of a transit route network, and in the timetabling and vehicle scheduling processes. Other changes are not required, but are advisable, using this opportunity upon the introduction of EB. The work covers the main characteristics of different types of EB with a short description, including the most popular charging technologies, and it presents the generally accepted transit operations planning process. Likewise, it describes and analytically formulates new challenges that arise when introducing EB. The outcome of the analyses shows that multiple new considerations must take place. It is also shown that the different charging techniques will influence the operations planning process in different ways and to a varying extent. With overnight, quick and continuous charging, the main challenges are in the network route design step, given the possibility of altering the existing network of routes, with efficient and optimal changes of the timetabling and vehicle scheduling components. An illustrative example, based on four bus lines in Norrköping, Sweden, is formulized and introduced using three problem instances of 48, 82, and 116 bus trips. The main results exhibit the minimum number of vehicles required using different scenarios of charging stations.
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| 4. |
- Häll, Carl Henrik, 1978-, et al.
(author)
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Adjustments of Public Transit Operations Planning Process for the Use of Electric Buses
- 2017
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In: TRB Annual Meeting Online, 2017. - : Transportation Research Board.
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Conference paper (peer-reviewed)abstract
- This work investigates and discusses how the introduction of electric buses (EB), both battery and plug-in hybrid EB, will and should change the operations planning of a public transit system. It is shown that some changes are required in the design of a transit route network, and in the timetabling and vehicle scheduling processes. Other changes are not required, but are advisable, using this opportunity upon the introduction of EB. The work covers the main characteristics of different types of EB with a short description, including the most popular charging technologies, and it presents the generally accepted transit operations planning process. Likewise, it describes and analytically formulates new challenges that arise when introducing EB. The outcome of the analyses shows that multiple new considerations must take place. It is also shown that the different charging techniques will influence the operations planning process in different ways and to a varying extent. With overnight, quick and continuous charging, the main challenges are in the network route design step, given the possibility of altering the existing network of routes, with efficient and optimal changes of the timetabling and vehicle scheduling components.
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| 5. |
- Quttineh, Nils-Hassan, 1979-, et al.
(author)
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Combined Timetabling and Vehicle Scheduling for Electric Buses
- 2017
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In: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China. - Hong Kong : HKSTS.
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Conference paper (other academic/artistic)abstract
- In this paper we present a novel mathematical model, integrating the timetabling and vehicle schedulingproblems for electric buses. The objective is to minimize the number of buses while satisfying constraintsconcerning routing and charging, including design choices of where to install charging equipment. Weillustrate the different effects of tackling the timetabling and vehicle scheduling of electric buses as separateproblems or as a joint problem, both for fixed and variable headways. To do so, tests are performed with: (i) given timetable, i.e. solving only the vehicle scheduling problem, (ii) fixed headways for each line, (iii) variable headways. For these tests, a small case based on four bidirectional bus lines is used.
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| 6. |
- Quttineh, Nils-Hassan, et al.
(author)
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Integrated solution for electric bus timetabling and vehicle scheduling combined with choices of charging locations
- 2023
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In: Journal of Public Transportation. - : ELSEVIER. - 1077-291X. ; 25
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Journal article (peer-reviewed)abstract
- This paper presents a novel mathematical model, integrating timetabling and vehicle scheduling problems for electric buses. The objective is to minimize the number of buses while satisfying constraints concerning routing and charging, including design choices for where to install charging stations. The aim of the paper is to illustrate and discuss the effects of solving the timetabling and vehicle scheduling of electric buses (including where to install charging infrastructure) separately, compared to solving them jointly in one single step. For that purpose, we perform tests with: i) given timetable, that is, solving only the vehicle scheduling problem, ii) fixed headways for each line, and iii) variable headways. A small test case based on actual bus lines from Va center dot stra Fro center dot lunda, Gothenburg, Sweden, is used. From the numerical experiments, we verify that combining the two planning steps can significantly reduce the number of vehicles needed.
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| 7. |
- Soroka, Inna, et al.
(author)
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Particle size effect of Ag-nanocatalysts deposited on carbon as prepared by γ-radiation induced synthesis
- 2020
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In: Radiation Physics and Chemistry. - : Elsevier. - 0969-806X .- 1879-0895. ; 169
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Journal article (peer-reviewed)abstract
- The effect of silver particle sizes on the catalytic performance of Ag/C electrodes for oxygen reduction reaction (ORR) was studied. The Ag particles were precipitated from AgNO3 solutions on Vulcan XC-72 carbon as support by γ-radiation induced synthesis method. The structural and morphological characterizations of the electrode materials were done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that particles with smaller diameters, 11 ± 6 nm, possess higher catalytic activity for ORR (50 mA/cm2 at 0.3 V) as compared to those with larger diameters, 41 ± 5 nm, ORR activity is 25 mA/cm2 at 0.3 V. The observed effect may be explained by an increased amount of low coordinated atoms in smaller particles as compared to the larger ones.
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