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| 7. |
- Ekberg, Christian, 1967, et al.
(författare)
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The structure of plutonium(IV) oxide as hydrolysed clusters in aqueous suspensions
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:6, s. 2035-2040
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of plutonium still puzzles scientists 70 years after its discovery. There are several factors making the chemistry of plutonium interesting including its ability to keep several oxidation states. Another unique property is that the oxidation states +III, +IV, +V and +VI may exist simultaneously in solution. Another property plutonium shares with some other tetravalent metal ions is the ability to form stable polynuclear complexes or colloids. The structures of freshly prepared and five-year old plutonium(IV) colloids are compared with crystalline plutonium(IV) oxide using Pu L-3-edge EXAFS. It was shown that as the plutonium colloids age they do in fact shrink in size, contrary to previous expectations. The aged colloidal particles are indeed very small with only 3-4 plutonium atoms, and with a structure very similar to solid plutonium(IV) oxide, but with somewhat shorter mean Pu-O bond and Pu. Pu distances indicating a partial oxidation. The very small size of the colloidal particles is further supported by the fact that they do not sediment on heavy ultra-centrifugation.
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| 8. |
- Ekberg, Christian, 1967, et al.
(författare)
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Uncertainties in chemical modelling of solubility, speciation and sorption
- 2011
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Ingår i: Accreditation and Quality Assurance. - : Springer Science and Business Media LLC. - 0949-1775 .- 1432-0517. ; 16:4-5, s. 207-214
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Tidskriftsartikel (refereegranskat)abstract
- Chemical analyses become more and more expensive to perform, and more and more research is based on numerical simulation. However, all numerical models are subject to uncertainties, either in the implementation of the model towards reality or simply that the desired input data are not explicitly known without uncertainties. These uncertainties will affect the predictability of any model and thus it is of vital interest that the effect of these uncertainties is known. Especially if the result of the simulations is a topic upon which serious decisions are going to be made. In this paper, we outline a simple and rather straight forward approach to the effect of uncertainties on such simple chemical calculations as solubility of a solid phase in a given water and the chemical speciation of a solution. In addition, we also touch upon the much more complicated matter of uncertainties in sorption modelling-a subject which will be enlightened in much greater detail in an upcoming NEA publication in the matter.
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| 9. |
- Fleischer, Siegfried, 1938-, et al.
(författare)
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Dark oxidation of water in soils
- 2013
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - Hoboken, NJ : Wiley-Blackwell. - 0280-6509 .- 1600-0889. ; 65:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the release of oxygen (O2) under dark conditions in aerobic soils. This unexpected process is hidden by respiration which constitutes the dominating reversal O2 flux. By using H218O in different soils, we confirmed that 16O18O and 18O2 released under dark soil conditions originated from added H218O. Water is the only large-scale source of electrons for reduction of CO2 in soils, but it has not been considered as an electron donor because of the very strong oxidation system needed. A high share of soil inorganic material seems to favor the release of O2. © 2013 S. Fleischer et al.
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| 11. |
- Hernandéz Solís, Augusto, 1980, et al.
(författare)
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Statistical uncertainty analyses of void fraction predictions using two different sampling strategies: Latin Hypercube and Random Sampling
- 2010
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Ingår i: ASME Conference Proceedings. 18th International Conference on Nuclear Engineering, Xian, 17-21 May 2010. - 9780791849323 ; 4:PARTS A AND B, s. 1059-1068
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Konferensbidrag (refereegranskat)abstract
- In recent years, a more realistic safety analysis of nuclear reactors has been based on best estimate (BE) computer codes. Because their predictions are unavoidably affected by conceptual, aleatory and experimental sources of uncertainty, an uncertainty analysis is needed if useful conclusions are to be obtained from BE codes. In this paper, statistical uncertainty analyses of cross-sectional averaged void fraction calculations using the POLCA-T system code, and based on the BWR Full-Size Fine-Mesh Bundle Test (BFBT) benchmark are presented by means of two different sampling strategies: Latin Hypercube (LHS) and Simple Random Sampling (SRS). LHS has the property of densely stratifying across the range of each input probability distribution, allowing a much better coverage of the input uncertainties than SRS. The aim here is to compare both uncertainty analyses on the BWR assembly void axial profile prediction in steady-state, and on the transient void fraction prediction at a certain axial level coming from a simulated re-circulation pump trip scenario. It is shown that the replicated void fraction mean (either in steady-state or transient conditions) has less variability when using LHS than SRS for the same number of calculations (i.e. same input space sample size) even if the resulting void fraction axial profiles are non-monotonic. It is also shown that the void fraction uncertainty limits achieved with SRS by running 458 calculations (sample size required to cover 95% of 8 uncertain input parameters with a 95% confidence), result in the same uncertainty limits achieved by LHS with only 100 calculations. These are thus clear indications on the advantages of using LHS.
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| 12. |
- Hernandéz Solís, Augusto, 1980, et al.
(författare)
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Statistical uncertainty analysis applied to the DRAGONv4 code lattice calculations and based on JENDL-4 covariance data
- 2012
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Ingår i: Proc. Int. Conf. on Advances in Reactor Physics – Linking Research, Industry, and Education (PHYSOR 2012), Knoxville, TN, USA, April 15-20, 2012, American Nuclear Society. - 9781622763894 ; 4, s. 2960-2974
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Konferensbidrag (refereegranskat)abstract
- In this paper, multi-group microscopic cross-section uncertainty is propagated through the DRAGON (Version 4) lattice code, in order to perform uncertainty analysis on k_inf and 2-group homogenized macroscopic cross-sections predictions. A statistical methodology is employed for such purposes, where cross-sections of certain isotopes of various elements belonging to the 172 groups DRAGLIB library format, are considered as normal random variables. This library is based on JENDL-4 data, because JENDL-4 contains the largest amount of isotopic covariance matrixes among the different major nuclear data libraries. The aim is to propagate multi-group nuclide uncertainty by running the DRAGONv4 code 500 times, and to assess the output uncertainty of a test case corresponding to a 17x17 PWR fuel assembly segment without poison. The chosen sampling strategy for the current study is Latin Hypercube Sampling (LHS). The quasi-random LHS allows a much better coverage of the input uncertainties than simple random sampling (SRS) because it densely stratifies across the range of each input probability distribution. Output uncertainty assessment is based on the tolerance limits concept, where the sample formed by the code calculations infers to cover 95% of the output population with at least a 95% of confidence. This analysis is the first attempt to propagate parameter uncertainties of modern multi-group libraries, which are used to feed advanced lattice codes that perform state of the art resonant self- shielding calculations such as DRAGONv4.
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| 13. |
- Hernandéz Solís, Augusto, 1980, et al.
(författare)
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Uncertainty and sensitivity analyses as a validation tool for BWR bundle thermal-hydraulic predictions
- 2011
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 0029-5493. ; 241:9, s. 3697-3706
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, more realistic safety analyses of nuclear reactors have been based on best estimate (BE) computer codes. The need to validate and refine BE codes that are used in the predictions of relevant reactor safety parameters, led to the organization of international benchmarks based on high quality experimental data. The OECD/NRC BWR full-size fine-mesh bundle test (BFBT) benchmark offers a good opportunity to assess the accuracy of thermal hydraulic codes in predicting, among other parameters, single and two phase bundle pressure drop, cross-sectional averaged void fraction distributions and critical powers under a wide range of system conditions. The BFBT is based on a multi-rod assembly integral test facility which is able to simulate the high pressure, high temperature fluid conditions found in BWRs through electrically heated rod bundles. Since code accuracy is unavoidably affected by models and experimental uncertainties, an uncertainty analysis is fundamental in order to have a complete validation study. In this paper, statistical uncertainty and sensitivity analyses are used to validate the thermal hydraulic features of the POLCA-T code, based on a one dimensional model of the following macroscopic BFBT exercises: (1) single and two phase bundle pressure drop, (2) steady-state cross-sectional averaged void fraction, (3) transient cross-sectional averaged void fraction and (4) steady-state critical power tests. The Latin hypercube sampling (LHS) strategy was chosen since it densely stratifies across the range of each uncertain input probability distribution, allowing a much better coverage of the input uncertainties than simple random sampling (SRS). The results show that POLCA-T predictions on pressure drop and void fractions under a wide range of conditions are within the validation limits imposed by the uncertainty analysis, while the accuracy of critical power predictions depends much on the boundary and input conditions.
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| 16. |
- Johnsson, Anna, 1975, et al.
(författare)
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Bioligand-mediated partitioning of radionuclides to the aqueous phase
- 2008
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 277:3, s. 637-644
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous-phase partitioning of 59Fe, 147Pm, 234Th and 241Am by complexing compounds from subsurface bacteria has previously been studied in the presence of quartz sand. In this study the aqueous-phase partitioning of pico- to submicromolar amounts of 59Fe, 147Pm, 234Th and 241Am was analyzed in the presence of TiO2 and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. TiO2, with BET surface area of 49.9 m2·g-1, was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After incubation, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation method. Two types of values were calculated: solution% = the activity maintained in solution relative to the total activity, and Q-values = the quotient between the activity in samples and the activity in controls. Aerobic supernatants had solution% values between 89% and 100% for 59Fe and between 18 and 43% for 234Th. The solution% values for 241Am and 147Pm were less than 2% overall, but the Q-values were between 34 and 115 times more 241Am in bacterial supernatants than in controls. The corresponding values for 147Pm ranged from 6 to 20 times more than in the control. The solution% values for all elements in the presence of anaerobic supernatants were below 2%, but the Q-values clustered around 7 for 59Fe and ranging from 2 to 29 for 234Th, indicated that anaerobic supernatants partitioned these elements to the aqueous phase. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed, using the Chrome Azurol S assay. Complexation with excreted organic ligands is most likely the reason for the higher amounts of metals in samples than in the controls. Hence, aerobically and anaerobically excreted organic ligands seem able to influence the mobility of radionuclides in aerobic and anaerobic environments contaminated with these compounds.
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| 17. |
- Johnsson, Anna, 1975, et al.
(författare)
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Leaching of spent nuclear fuel in the presence of siderophores
- 2009
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 279:2, s. 619-626
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Tidskriftsartikel (refereegranskat)abstract
- Metal species that are dissolved in water can be transported in the environment, because they can be mobile. Microorganisms can affect metal mobility by excreting organic ligands with high metal affinity. Siderophores are organic ligands with high affinities for Fe 3+ . They are also able to form complexes with other metals such as actinides. Many countries plan to deposit spent nuclear fuel in deep geological repositories. Microorganisms are present in these subterranean environments and could potentially affect the repository. In this study, the effect of microbial siderophores on the dissolution behavior of two fragments of a spent nuclear fuel pellet was investigated. The commercial hydroxamate siderophore, deferoxamine mesylate (DFAM), and pyoverdin siderophores, isolated from cultures of Pseudomonas fluorescens (CCUG 32456A), were used. DFAM and lyophilized pyoverdins were dissolved in synthetic groundwater to final concentrations of 10 μM and 2.5·10 -2 g·L -1 , respectively. The fuel pellet fragments were kept in sealed pressure vessels at 10 bars of H 2 . The pyoverdin solution was first tested, followed by the DFAM solution and the pure synthetic groundwater. Samples were taken on 0, 1, 5, 9 and 14 days after changing the solution in the pressure vessels. The elemental composition of samples was analyzed by means of ICP-MS. The pyoverdin solution maintained significantly higher concentrations of Np and Pu than the pure synthetic groundwater. On the 14 th day the concentrations of Np and Pu in the pure synthetic groundwater were 0.01 nM and 0.13 nM, respectively, compared to 0.02 nM and 0.31 nM in the pyoverdin solution. Furthermore, spent nuclear fuel samples were observed to release Ru in the presence of both pyoverdin and DFAM. Hence, it seems that siderophores can form complexes with elements present in spent nuclear fuel. © 2008 Akadémiai Kiadó.
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| 18. |
- Johnsson, Anna, 1975, et al.
(författare)
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Solid-aqueous phase partitioning of radionuclides by complexing compounds excreted by subsurface bacteria
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23(8), s. 621-630
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Tidskriftsartikel (refereegranskat)abstract
- Radionuclides are present in numerous aerobic and anaerobic subsurface environments due to nuclear weapons testing, leakage from process and storage facilities, and discharge of radioactive waste. The partitioning of radionuclides between liquid and solid phases by complexing compounds excreted by subsurface bacteria was studied. The solid-aqueous phase partitioning of pico- to submicromolar amounts of 59 Fe, 147 Pm, 234 Th, and 241 Am was analyzed in the presence of quartz sand and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions, and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. Quartz sand, with a Brunauer, Emmett, and Teller (BET) surface area of 0.1 m 2 g -1 , was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After centrifuging, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation. Relative to the control, aerobic supernatants maintained more than 50% of the added 59 Fe, 234 Th, and 241 Am. The highest amount of metal present in the liquid phase of the anaerobic supernatants was found in the case of 241 Am, with 40% more 241 Am in samples than in controls. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed using the Chrome Azurol S assay. The great amounts of radionuclides in the liquid phases of samples were likely due to complexation with such compounds. Bacterially excreted complexing compounds hence seem able to influence the solid-aqueous phase partitioning of radionuclides. This could influence the mobility of radionuclides in contaminated subsurface environments.
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| 19. |
- Kalinowski, Birgitta E., 1900, et al.
(författare)
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Microbial leaching of uranium and other trace elements from shale mine tailings at Ranstad
- 2004
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Ingår i: Geoderma. - : Elsevier BV. - 0016-7061. ; 122:2-4, s. 177-194
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Tidskriftsartikel (refereegranskat)abstract
- High levels of heavy metals have been found in the surroundings of the closed uranium (U) mine in Ranstad in southern Sweden. These findings cannot be explained entirely by abiotic processes. It was not until recently that biology was taken into account in the discussion about mobilization of metals at this site. It is well known that bacteria produce short-chain organic acids and element-specific ligands (siderophores) that are able to change pH and enhance chelation, which results in increased mobilization of many trace elements. Other (nonessential) elements, such as thallium (Tl), lanthanides, and actinides, may also be mobilized as a result of such bacterial action. This paper describes the mobilization of U and other elements from U ores by bacteria. Three common siderophore-producing bacterial species, Pseudomonas fluorescens, Shewanella putrefaciens and Pseudomonas stutzeri, were incubated in a chemically defined medium supplemented with tailings material with a content of 0.0013% U by weight, which had been exposed to natural weathering for 30 years. Nonleached U ore (0.61% U by weight) from the same area was incubated with P. fluorescens and S. putrefaciens for comparison. P. fluorescens grown with ore caused a change in pH in the growth medium from 4.7 to 9.3, which was significantly higher than for the other two species, for which pH was about 5.2. P. fluorescens was the only species that thrived and mobilized measurable amounts of U from the two ores, leaching out 0.0010.005% of the total amount of U from both. The release of U is attributed to the production of pyoverdine chelators, since U could not be detected either in sterile controls or in the experiments with the other two bacteria. P. fluorescens also doubled the chromium (Cr) concentration in solution as compared with the sterile controls, whereas P. stutzeri and S. putrefaciens caused a five to sixfold increase in Cr concentration. Thallium, cobalt (Co), zinc (Zn), manganese (Mn), and vanadium (V) concentrations initially resembled those in the sterile controls, but from day 2 of the experiment, a decrease was observed. The difference in leaching behavior between the bacteria used in this study is likely to have been due to the production of different chelators rather than being an effect of pH, since many metals have low solubility at neutral to alkaline pH. This study using laboratory incubations shows that mobilization of U from ore can occur aerobically at neutral to alkaline conditions, which may be an important process behind the high content of heavy metals in the surroundings of the closed U mine at Ranstad.
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| 20. |
- Kalinowski, Birgitta E., et al.
(författare)
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Microbial mobilization of uranium from shale mine waste
- 2006
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Ingår i: Geomicrobiology Journal. - : Informa UK Limited. - 0149-0451 .- 1521-0529. ; 23:3-4, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- The alum shale in the Billingen area in southern Sweden was mined in Ranstad for 5 years during the 1960s. The crushed tailings (processed and unprocessed) were left behind when the Ranstad mine was closed that has caused leaching of metals to the surroundings. The siderophore producing bacterium Pseudomonas fluorescens (sp, SE Sweden) was grown in batch cultures for 5 to 8 days with naturally weathered (unprocessed) uranium ore (0.0029% U by weight), kolm (0.52% U by weight) and acid-leached ore (0.0099% U by weight) in chemically defined media (unbuffered and buffered). Pseudomonas fluorescens grown with ore and unbuffered medium changed the pH from 4.7 to 9.3 and leached out 0.016 to 0.9% (normalized to surface area) of the total amount of U from the different ores. Incubation of the acid-leached ore with bacteria in buffered medium leached out 0.04% of the total U. Uranium was leached out selectively at all conditions, but this could be a pH effect, as pH increased at the same time as the U concentrations did. The observed release of Fe was most likely attributed to the production of microbial siderophores (Fe3+ specific chelators) since Fe3+ has a low solubility at pH > 4. As siderophores contain a number of chelating groups they may still function as complexators even in partly degraded form also for other metals than Fe. Thus, the production of microbial chelators could contribute to the elevated metal concentrations in the drainage water from the closed Ranstad mine, as abiotic processes cannot fully explain these high metal concentrations. In the extension: ligand promoted leaching of toxic elements could also be the key to bioremediation as there is a need for nontoxic cleanup methods for metal contaminated sites.
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| 21. |
- Larsson, Kristian, 1982, et al.
(författare)
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Dissolution and characterization of HEV NiMH batteries
- 2013
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 33:3, s. 689-698
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Tidskriftsartikel (refereegranskat)abstract
- Metal recovery is an essential part of the recycling of hybrid electric vehicle battery waste and the first step in a hydrometallurgical treatment is dissolution of the solid material. The properties of separated battery electrode materials were investigated. Focus was put on both the solid waste and then the dissolution behaviour. The cathode contains metallic nickel that remains undissolved when utilizing non-oxidizing conditions such as hydrochloric or sulphuric acid in combination with a low oxygen atmosphere. In these conditions the cathode active electrode material is fully dissolved. Not dissolving the nickel metal saves up to 37% of the acid consumption for the cathode electrode material. In the commonly used case of oxidizing conditions the nickel metal dissolves and a cobalt-rich phase remains undissolved from the cathode active material. For the anode material a complete and rapid dissolution can be achieved at mild conditions with hydrochloric, nitric or sulphuric acid. Optimal parameters for all cases of dissolution was pH 1 with a reaction time of approximately >= 20,000 s.
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| 22. |
- Larsson, Kristian, 1982, et al.
(författare)
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Selective Dissolution of Electrode Materials from NiMH Batteries
- 2010
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Ingår i: Proceedings of Hydroprocess 2010 the 3rd International Workshop on Process Hydrometallurgy.
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Konferensbidrag (refereegranskat)abstract
- Nickel-metal hydride (NiMH) batteries are one of the mostcommon battery types used in hybrid electric vehicles (hev).The electrodes of these batteries contain large amounts ofnickel, cobalt and rare earth metals. Recovery of these metals is economically and environmentally beneficial as it mines an easily accessible source of raw material. Recovery should be performed using a method which minimizes the use of energy and chemicals.One way to perform the recovery is to selectively dissolveelectrode materials during hydrochemical processing. In the case of NiMH batteries, the positive electrode active material, nickel hydroxide, can be dissolved without dissolving the electrode backing material (usually nickel metal). To rapidly dissolve all of the nickel hydroxide, and as little as possible of the nickel metal,becomes an optimization problem: where is the suitable point at which to stop dissolving material in combination with the choice of chemical surrounding Experiments were performed with a temperature controlled by pH-stat, which maintains a constant pH during dissolution. This work shows that rapid dissolution of the active material on the positive electrode can be achieved at a low temperature and a relatively low acid concentration (pH 0.5 –1.5) whilst leaving the major part of the nickel metal undissolved. This is possible with all three tested minerals: acidsnitric, sulphuric and hydrochloric. The speed of dissolution is mostly affected by the pH and only slightly affected by the type of acid. Therefore the most suitable acid depends on the choice of process following the dissolution.
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| 23. |
- Larsson, Kristian, 1982, et al.
(författare)
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Using Cyanex 923 for selective extraction in a high concentration chloride medium on nickel metal hydride battery waste
- 2012
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X. ; 129, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- The extraction properties of the solvating extractant trialkylphosphine oxide mixture Cyanex 923 have been investigated using liquid-liquid extraction methods on leach liquors from nickel metal hydride batteries dissolved in 8 M hydrochloric acid. Separation routes for leach liquors from individual electrode materials and a mixed material were developed. The batteries used in this study contained thirteen metals and the developed separation schemes separate them in up to four fractions. The main fraction in each case contains nickel, also potassium and magnesium if present in the feed. Part of the nickel raffinate is refluxed to the dissolution step in order to reduce the amount of metals to be extracted into the organic phase. A nitrate strip step separates the cobalt and manganese from the lanthanoid content, since lanthanoid nitrate complexes are extracted.
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| 24. |
- Larsson, Kristian, 1982, et al.
(författare)
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Using Cyanex 923 for selective extraction in a high concentration chloride medium on nickel metal hydride battery waste Part II: mixer-settler experiments
- 2013
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X. ; 133, s. 168-175
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Tidskriftsartikel (refereegranskat)abstract
- Nickel metal hydride batteries are extensively used throughout society and represent a large and complex metallic mixture requiring recycling. This paper deals with the recovery and separation of metals from nickel metal hydride battery waste dissolved in 8 M hydrochloric acid. Three processes based on leachates from individual electrode materials and a mixed material have been evaluated using mixer-settlers. The solvating extractant used is the trialkylphosphine oxide mixture Cyanex 923. The batteries used in this study contained thirteen metals and the processes separate them in up to four fractions. The main fraction in each process successfully creates a high-concentration nickel stream with low levels of potassium and magnesium (if present in the feed) by extracting the other metals. The purity of the nickel stream after the main process step (4-5 stages) is >99.9%, excluding magnesium and potassium. The extracted metals are separated using a nitrate strip, which allows the rare earth metals and aluminium to be separated from cobalt and manganese.
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| 25. |
- Meinrath, Gunther, et al.
(författare)
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Sorption of Iron on Surfaces: Modelling, Data Evaluation, and Measurement Uncertainty
- 2004
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Ingår i: Acta Hydrochimica et Hydrobiologica. - : Wiley. - 1521-401X .- 0323-4320. ; 32:2, s. 154-160
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Tidskriftsartikel (refereegranskat)abstract
- Assessment of the likely outcome of engineered invention strategies in acid mine drainage often involves complex geochemical modelling activities. Geochemical modelling is based on chemical thermodynamic data. In addition sorption models, kinetical reaction rates and transport tools are included into the modelling codes because the interactions between solution components and surfaces, reaction time and transport are considered important features characterising the site-specific situation. In the determination of both thermodynamic data and sorption coefficients, speciation calculations play an important role. By applying the probabilistic speciation code Ljungskile to some simplified acid mine drainage scenarios, the strong impact of chemical speciation on the complete measurement uncertainty budget of geochemical modelling predictions is shown. The complete measurement uncertainty budget in combination with other metrological concepts like traceability is an essential element of quality assurance for experimental data. The elements of quality assurance are provided by international agreements and normative documents on national and international levels. The following discussion will focus on some metrological issues of sorption data.
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| 26. |
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| 27. |
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| 28. |
- Skarnemark, Gunnar, 1948, et al.
(författare)
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Production of Rh-103m for cancer therapy
- 2009
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 280:2, s. 371-373
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Tidskriftsartikel (refereegranskat)
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| 29. |
- Skarnemark, Gunnar, 1948, et al.
(författare)
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SIMSISAK–a Method to Model Nuclide Transport in the SISAK System
- 2019
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 37:3-4, s. 232-244
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Tidskriftsartikel (refereegranskat)abstract
- A computer model that calculates the transport yield of a nuclide through an arbitrary SISAK experimental set-up has been developed. The model is intended to be used for two types of calculations connected to chemical studies of the heaviest elements. If the production cross section and the nuclide half-life are known, it can be used to estimate the number of decay events to be expected at the detection site. Consequently, if the number of atoms decaying in the detection cells is known, it can be used to estimate the production cross section or the half-life, provided that one of these properties is known.
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| 30. |
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| 31. |
- Ödegård Jensen, Arvid, 1968, et al.
(författare)
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Propagating non-normally distributeduncertainty-The Ljungskile code
- 2006
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Ingår i: International workshop combining and reporting analytical results:the role of tracability and uncertainty for comparing analytical results, conference proceedings. ; , s. 154-160
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 32. |
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| 33. |
- Ödegård Jensen, Arvid, 1968, et al.
(författare)
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Testing of uranium dioxide containing different levels of alpha activity under anaerobic and reducing conditions
- 2008
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Ingår i: Materials Research Society Symposium Proceedings. - 0272-9172. - 9781605110745 ; 1104, s. 115-120
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Konferensbidrag (refereegranskat)abstract
- Samples of UO2 containing 5% 235U and 0, 5, or 10% 233U were tested in a dilute simulated groundwater using N 2 or H2 gas as the atmosphere. Some tests included metallic iron in the solution. Each test condition used samples run in triplicate for at least 21 days and each test condition was run for two consecutive test periods. The results show that the dissolution behavior of the samples is the same in both N2 and H2 atmospheres. The amount of U dissolved under these conditions clearly showed the enhancement of dissolution due to oxidation of the sample surface by radiolysis products for conditions without metallic Fe. When a piece of iron was included in the bottom of the test vessel, the amount of dissolution decreased dramatically indicating that the Fe(II) ions released from the corroding iron were able to react with most of the radiolysis products before they could oxidize the UO2 surface.
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| 34. |
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