| 1. |
- Andersson, Sofie, 1976, et al.
(författare)
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Berkelium nitrate complex formation using a solvent extraction technique
- 2006
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 94:1, s. 59-61
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Tidskriftsartikel (refereegranskat)abstract
- The extraction of Bk(III) into an organic phase consisting of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine, 2-bromodecanoic acid and tert-butyl benzene as a function of nitrate ion concentration in the aqueous phase was studied in order to determine the stability constants of the formation of Bk nitrate complexes. Increasing the nitrate ion concentration in the aqueous phase will increase the nitrate complex formation and thus the extraction of metal ions will decrease. Measuring this decrease in distribution ratio and fitting the data points with an appropriate model gives the stability constants of the Bk nitrate complex formation. © by Oldenbourg Wissenschaftsverlag.
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| 2. |
- Andersson, Sofie, 1976, et al.
(författare)
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Study of nitrate complex formation with Pm, Eu, Am and Cm using a solvent extraction technique
- 2004
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 92:12, s. 863-867
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Tidskriftsartikel (refereegranskat)abstract
- The separation of actinides and lanthanides is an important question in the treatment of spent nuclear fuel in the transmutation concept. To find an efficient and well functioning separation process it is necessary to study the chemistry of the elements in the two groups in different aqueous media. The stability constants of the nitrate complex formation with Pm, Eu, Am and Cm were determined using solvent extraction. The extraction was studied using the synergistic system of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine and 2-bromodecanoic acid in tert-butyl benzene. As the nitrate ion concentration in the aqueous phase was increased, a decrease in separation between actinides and lanthanides was seen owing to complex formation between the different elements and the nitrate ions.
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| 3. |
- André, Magnus, et al.
(författare)
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Measuring sorption coefficients and BET surface areas on intact drillcore and crushed granite samples
- 2008
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 96:9-11, s. 673-677
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Tidskriftsartikel (refereegranskat)abstract
- In general sorption coefficients, K-d cat ion exchange capacity, CEC, and BET surface areas are measured on crushed rock samples because it is very time consuming to measure K-d and CEC on larger rock pieces as it takes a long time for the sorbing species to penetrate into and equilibrate a large sample. Also conventional sample holders for BET measurements are too small to hold a large sample. We have manufactured large sample holders for BET measurements and modified the equipment so that it is possible to measure BET surface areas on samples with 50 mm diameter and LIP to 100 mm length. Results are presented for intact pieces and compared to results on crushed material from the same drillcore. For K-d and CEC measurements we have developed a technique and equipment by which ions can be made to rapidly intrude into and equilibrate the internal surfaces of the same size samples as mentioned above. The method is based on electro-migration where the sample is placed between two vessels one with an anode and other with a cathode. The electric potential gradient drives the ions into and through the sample very much faster than molecular diffusion does. With Cs as the sorbing ion a few weeks were sufficient to equilibrate the 50 mm long sample. In previous diffusion experiments it took more than a year to equilibrate a 15 mm thick sample. A special mixing technique eliminates the development of low and high PH in the electrode compartments. K-d results from measurements on an intact drillcore are presented and comparison is made with results obtained on crushed material from the same bore core. The results from the sorption experiments are compared with the results from the BET surface area determinations in an attempt to evaluate the use of the BET surface area as a proxy for sorption behaviour.
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| 4. |
- Brown, Paul L., et al.
(författare)
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The aqueous chemistry of radium
- 2022
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 110:6-9, s. 505-513
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Tidskriftsartikel (refereegranskat)abstract
- Available literature data on the aqueous chemistry of radium are compiled. There are limited available experimental data and a significant portion of the data has been estimated using electrostatic techniques, typically based on the corresponding data of barium. The available data are compared with the corresponding data of barium (and strontium) and a methodology for estimating additional radium thermochemical data is described.
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| 5. |
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| 6. |
- Fawzy Abdel-Magied, Ahmed
(författare)
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Solid phase extraction of uranium from phosphoric acid : kinetic and thermodynamic study
- 2017
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 105:10, s. 813-820
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Tidskriftsartikel (refereegranskat)abstract
- There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPATOPO@MCM-41 (mass ratio 2: 1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg. 1 min. 1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H-3 PO4 is an exothermic and spontaneous process.
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| 7. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of C5-BTBP in cyclohexanone irradiated in the absence and precence of an aqueous phase
- 2012
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 100:4, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Spent nuclear fuel contains many highly ra-dioactive species; hence solvents used in reprocessing willbe subjected to radiolysis. In this study, solvents containingone of the BTBP molecules intended for the separation oftrivalent actinides and lanthanides, the so called C5-BTBP,have been subjected to radiolysis and hydrolysis. We presenthere that this compound shows a dramatic decrease in bothdistribution ratios and separation factor when irradiated withhigher doses up to 50 kGy; particularly in the presence ofan aqueous phase. Furthermore, fast hydrolytic degradation isobserved, which significantly contributes to the overall degreeof decomposition. This is supported by speciation studies per-formed by HPLC and LC-MS methods. Proposed structuresof the highest-yield degradation products are presented andthey seem to confirm previously drawn structures for theseproducts. From these studies it can be concluded that thepresence of nitric acid or nitrate during irradiation leads tohigher content of species containing keto groups.
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| 8. |
- Hedström, Hanna, 1983, et al.
(författare)
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Radon capture with silver exchanged zeolites
- 2012
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 100:6, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- To enable laboratory work with larger amounts of Ra-226 and its decay products, e.g., Rn-222 and its daughters, these need to be captured in order to avoid unnecessary alpha contamination of the laboratory work space and ventilation systems. In this study, radon gas was pumped through a column filled with the silver exchanged zeolite called "silver exchanged molecular sieves 13X" (Ag84Na2[(AlO2)(86)(SiO2)(106)]. xH(2)O). After exposure to radon, the radioactivity of the zeolite was measured repeatedly using high resolution gamma spectrometry. It was shown that radon was captured and retained in the silver exchanged zeolite. The zeolites' ability to retain radon was decreased by formation of metallic silver, caused by ionizing radiation. However, the zeolite was regenerated by heating and its radon capture ability was restored. The daughters of radon are not in gas phase and will hence stay on the column.
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| 9. |
- Hill, C., et al.
(författare)
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Assessment of ligand extraction properties: an intercomparison campaign amongst EUROPARTners
- 2008
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 96:4-5, s. 259-264
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Tidskriftsartikel (refereegranskat)abstract
- An intercomparison campaign was organized at the beginning of the European FP6 EUROPART Integrated Project, among the partners involved in the assessment of the extracting properties of novel ligands, in order to check their accuracy and reliability when determining metal cation distribution ratios. Three different extracting systems, presenting various selectivity and affinity towards trivalent actinides were selected: (i) CMPO, (ii) TPTZ and (iii) BTP. Although some differences could be pointed out in the implementation of liquid-liquid extraction tests, the distribution ratios measured by the nine partners were fairly reproducible (
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| 10. |
- Jansson, Mats, et al.
(författare)
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CHEMLAB - in situ diffusion experiments using radioactive tracers
- 1998
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Ingår i: Radiochimica Acta. - 0033-8230 .- 2193-3405. ; 82, s. 153-156
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Tidskriftsartikel (refereegranskat)abstract
- In situ diffusion experiments in bentonite clay have been carried out in the probe CHEMLAB, using the radioactive tracers Co-57, Sr-85 and Cs-134. The measured diffusion profiles for the radionuclides are in good agreement with predicted profiles obtained from modelling based on apparent diffusivities and sorption coefficients obtained in laboratory experiments with corresponding clay density and ground water composition.
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