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- Fermvik, Anna, 1978, et al.
(författare)
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Influence of dose rate on the radiolytic stability of a BTPB solvent for actinide(III)/lanthanide(III) separation
- 2009
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 97:6, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The recently developed ligand MF2-BTBP dissolved in cyclohexanone is a promising solvent for the group separation of trivalent actinides(III) from the lantha-nides(III). Its high stability against nitric acid has been demonstrated recently. Since the solvent is also exposed to a continuously high radiation level in the counter current process, the radiolytic stability of the solvent was examined in this study. Irradiation experiments were carried out up to an absorbed dose of 100 kGy and the effect of the dose rate was investigated. The extraction behaviour for An(III)/Ln(III) separation was studied after radiolysis for evaluation. It was found that during high dose rate irradia-tion the extraction efficiency for both Am(III) and Eu(III) decreased significantly with increasing absorbed dose, whereas during the low dose rate irradiation the extraction efficiencies remained more or less at the same level.
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- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of solvents containing C5-BTBP: identification of degradation products and their dependence on absorbed dose and dose rate
- 2009
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Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 32, s. 6421-6430
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Tidskriftsartikel (refereegranskat)abstract
- Solvents intended for the separation of trivalent actinides from trivalent lanthanides in spent nuclear fuel have been irradiated with gamma-radiation. The solvents initially contained 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone and they were exposed to doses up to 20 kGy. Identification of degradation products was done using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Structures were suggested for a number of degradation products and the relative intensity of the peaks in the MS spectra was estimated. It was clear that the content of the original molecule, C5-BTBP, decreased with dose, while the content of the various degradation products increased. It was also shown that both the choice of diluent and the dose rate (Gy/h) affect the amount of degradation products formed. A degradation scheme was proposed for the radiolytic degradation of C5-BTBP.
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- Retegan Vollmer, Teodora, 1979, et al.
(författare)
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Electrospray Ionization Mass Spectrometry Investigation of BTBP - Lanthanide(III) and Actinide(III) Complexes
- 2009
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 27:5-6, s. 663-682
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Tidskriftsartikel (refereegranskat)abstract
- In the framework of nuclear waste reprocessing, the separation processes of minor actinides from fission products are developed using liquid-liquid extraction. To gain an understanding of the mechanism involved in the extraction process, a complex formation of actinides and lanthanides with BTBPs (6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines) was characterized using the Electrospray Ionization Mass Spectrometry (ESI-MS) technique. This study was carried out to compare the influence of diluents and side groups of the extractants on complex formation. Three different diluents, nitrobenzene, octanol and cyclohexanone, and two extractants, C5-BTBP and CyMe4-BTBP, were selected for this experiment. It was found that the change of the diluent and of the substituent on the BTBP moiety does not modify the stoichiometry of the complexes which is L2M(NO3)3. It is proposed that one nitrate is directly coordinated to the metal ion, the two other anions probably remaining in the outer coordination sphere. The difference observed in extracting properties is probably due to the solvation of the complexes by the diluent. The noncovalent force that holds complexes together are likely to be largely governed by electrostatic interactions even if the hydrophobic exterior of the complexes plays an important role in the complexation/extraction mechanism. The study of the stability of the ions in the gas phase shows that the C5-BTBP ligand has a labile hydrogen atom, which is a fragility point of C5-BTBP.
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- Retegan Vollmer, Teodora, 1979, et al.
(författare)
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Extraction of actinides with different 6,60-bis(5,6-dialkyl-[1,2,4]-triazin-3-yl)[2,20]-bipyridines (BTBPs)
- 2007
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Ingår i: SOLVENT EXTRACTION AND ION EXCHANGE. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 25:4, s. 417-431
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Tidskriftsartikel (refereegranskat)abstract
- The extraction of Am(III), Th(IV), Np(V), and U(VI) from nitric acid by 6,6′‐bis(5,6‐dialkyl‐[1,2,4]‐triazin‐3‐yl)‐[2,2′]‐bipyridines (C2‐, C4‐, C5‐, and CyMe4‐BTBP) was studied. Since only americium and neptunium extraction was dependent on the BTBP concentration, computational chemistry was used to explain this behavior. It has been shown that the coordination of the metal played an important role in forming an extractable complex into the organic phase, thus making it possible to extract pentavalent and trivalent elements from tetravalent and hexavalent elements. This is very important, especially because it shows other possible utilizations of a group of molecules meant to separate the actinides from the lanthanides. In addition, the level of extraction at very low or no BTBP concentration was explained by coordination chemistry.
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| 18. |
- Retegan Vollmer, Teodora, 1979
(författare)
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Investigations of Solvent Systems Based on bis-triazine-bipyridine (BTBP) - class Ligands for the Separation of Actinides from Lanthanides
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shortages of fossil fuel and other political movements contributed to the nuclear energy “renaissance”.Nuclear energy, however, is not free of challenges, one of them being nuclear waste management. The “once-through” cycle, where the nuclear fuel is used once in the reactor, cooled and finnaly disposed for about 100 000 years is currently used in most of the world. Reprocessing is another alternative, by making new fuel from separated uranium, MOX (Mixed Oxyde fuel). However, the storage time remains the same.An alternative to the storage time and radiotoxicity is partitioning and transmutation (P&T) concept. Transmutation is defined as the transformation of one radionuclide into another by changing its nuclear structure. The partitioning is the process of separation nuclides from the rest of the waste and involves a separation process which utilize an organic solvent containing one or several molecules and a diluent for extraction purposes. Among the last extractant families developed in Europe, used for partitioning, the 6,6’-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-[2,2’]bipyridine (BTBP) is the most promising molecule for an eventual industrial application. The present work focuses on several aspects insufficiently studied before in relation to a BTBP based extraction system. These aspects include: the importance of the diluents regarding both the extraction capabilities of the formed system with different metals, the role of the diluents in complex formation , the importance of the side groups added to the molecule to facilitate dissolution, easing the phase transfer and thus enhancing the extraction capabilities and also the role of the side groups in complex formation.
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- Retegan Vollmer, Teodora, 1979
(författare)
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The influence of Diluents and Side Groups of the Ligands on Liquid-Liquid Extraction of Actinides and Lanthanides
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil fuels are no longer a choice for energy production, both because of their diminishing availability and the bi-products of their combustion processes. A possibility to replace the fossil fuels would be utilization of nuclear power. No green-house gases are produced, but as any industry, it generates wastes.A proper plan for reusing valuable nuclides, both by preparing another kind of fuel or by transmutation, which, besides transforming the long-lived nuclides into short-lived ones, generates energy, seem to be P&T (partitioning and transmutation).The partitioning is the process of separation nuclides from the rest of the waste and involves a separation process which utilize an organic solvent containing one or several molecules and a diluent for extraction purposes.Among the last extractant families developed in Europe, 6,6’-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-[2,2’]bipyridine (BTBP) is the most promising molecule for an eventual industrial application. The present work focuses on several aspects insufficiently studied before and concerns strictly the BTBP family. The importance of the diluents regarding both the extraction capabilities of the formed system and the role of the diluents in protecting the molecule against radiolysiswithout adding a scavenging molecule will be discussed. The importance of the side groups added to the molecule first to facilitate dissolution, easing the phase transfer and thus enhancing the extraction capabilities and the role the side groups, in protecting the molecule against the radiolysis will also be discussed.Keywords: liquid-liquid extraction, Am, Eu, radionuclides, irradiation, side group, diluents.
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| 21. |
- Ahlström, Per-Erik, et al.
(författare)
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- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)
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