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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.

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.

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.

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.

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 Fe3+. 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 H2. 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 14th 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.

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.

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 (Aspo, 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 (Fe 3+ specific chelators) since Fe 3+ 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

When studying actinides or other elements with different possible oxidation states it is important to control which state is present in solution. Earlier redox control has been done by adding some other element to the solution but this approach introduces additional uncertainties. Since the sixties the AKUFVE apparatus has been used for precise solvent extraction studies. Now this equipment has been improved with redox control facilities, additional thermal control, and all parts in contact with the liquids are made of polyetherether ketone (PEEK) to minimize sorption.

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 0.001–0.005% 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.

We report the release of oxygen (O 2 ) under dark conditions in aerobic soils. This unexpected process is hidden by respiration which constitutes the dominating reversal O 2 flux. By using H 2 18 O in different soils, we confirmed that 16 O 18 O and 18 O 2 released under dark soil conditions originated from added H 2 18 O. Water is the only large-scale source of electrons for reduction of CO 2 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 O 2 . Keywords: dark water oxidation, soil CO 2 reduction, soil oxygen release, soil respiration (Published: 20 December 2013) Citation: Tellus B 2013, 65 , 20490, http://dx.doi.org/10.3402/tellusb.v65i0.20490 To access the supplementary material to this article, please see Supplementary files under Article Tools online.

The structure and orientation of semiflexible chain molecules in a shear flow field were studied by Brownian dynamics simulation. Molecules in the size range 200 nm to 1 μm were modeled as chains of spherical subunits with parameters chosen to mimic the size and persistence length of B-DNA. The analysis of the steady-state orientation showed a rather broad and asymmetric distribution. The simulations also showed that the orientation of the largest main axis of the moment of inertia tensor is significantly higher compared to the orientation obtained from averaging over the individual bonds in the molecules, the latter procedure being the relevant case when comparing with, e.g., linear dichroism experiments.

Sweden plans to dispose of spent nuclear reactor fuel in a deep geologic repository in granitic rock. The conditions in the repository in the long term will be reducing and water is not expected to contact the fuel until after more than 1000 years. At that time, most of the beta- and gamma-active nuclides will have decayed away and the radiation will be dominated by alpha decay. In order to simulate the radiolysis field for dissolution of spent fuel with age more than 1000 years we have used uranium dioxide containing 5% U-235 and 0, 5, or 10% U-233. The 10% U-233 gives an alpha activity appropriate to about 3000 years after disposal. Samples were testied in a synthetic groundwater with low ionic strength and with the chemical composition dominated by sodium bicarbonate and calcium chloride. Tests were run in triplicate using an atmosphere of nitrogen (1atm), hydrogen (10 bar), hydrogen (10 bar) plus an iron strip in the solution, nitrogen (1 atm) plus an iron strip in the solution, hydrogen (10 bar) plus an iron strip in the solution, hydrogen (10 bar) without the iron strip. Each of these test conditions was run for 2 consecutive periods of at least 21 days. The results showed that the dissolution behavior of the samples was the same for both nitrogen atmosphere and hydrogen atmosphere. The amount of U dissolved under these conditions clearly showed the enhancement of dissolution due to oxidation of the sample surface by radiolysis products. When an iron strip was added to the solution, 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 uranium dioxide surface.

Speciation calculations are often the base upon which further and more important conclusions are drawn, e.g., solubilities and sorption estimates used for retention of hazardous materials. Since speciation calculations are based on experimentally determined stability constants of the relevant chemical reactions, the measurement and experimental uncertainty in these constants will affect the reliability of the simulation output. The present knowledge of the thermodynamic data relevant for predicting the behaviour of a complex chemical system is quite heterogeneous. In order to predict the impact of these uncertainties on the reliability of a simulation output requires sophisticated modelling codes. In this paper, we will present a computer program, LJUNGSKILE, which utilises the thermodynamic equilibrium code PHREEQC to statistically calculate uncertainties in speciation based on uncertainties in stability constants. A short example is included.

In order to investigate the dissolution of plutonium(III) under reducing condition and in a carbonate rich water solid phases of plutonium hydroxide and carbonate were made. The still wet solid phases were placed in vessels which contained 1 M NaClO4. The atmosphere in the vessels was either H2 or a mixture of H2 and 0.03% CO2.The preliminary results shows that after some time the plutonium concentration in the solutions reached a value between 10−9 M and 10−7 M. The pH in the solutions is dependent of the atmosphere. In a pure H2 atmosphere the pH is changing over time whereas in the H2+CO2 atmosphere the pH stays between 7 and 7.5. At pH 8 the total carbonate concentration in the water was between 10−4 M and 10−3 M. This is the same order of magnitude as the ground water surrounding the proposed repository.

Sweden plans to dispose of spent nuclear fuel in a deep geologic repository in granitic rock. The disposal conditions allow water to contact the canisters by diffusion through the surrounding bentonite clay layer. Corrosion of the canister iron insert will consume oxygen and provide actively reducing conditions in the fluid phase. Experiments with spent fuel have been done to determine the dissolution behavior of the fuel matrix and associated fission products and actinides under conditions ranging from inert atmosphere to reducing conditions in solutions. Data for U, Pu, Np, Cs, Sr, Tc, Mo, and Ru have been obtained for dissolution in a dilute NaHCO3groundwater for 3 conditions: Ar atmosphere, H2atmosphere, and H2atmosphere with Fe(II) in solution. Solution concentrations forU, Pu, and Mo are all significantly lower for the conditions that include Fe(II) ions in the solutions together with H2atmosphere, while concentrations of the other elements seem to be unaffected by the change of atmospheres or presence of Fe(II). Most of the material that initially dissolved from the fuel has reprecipitated back onto the fuel surface. Very little material was recovered from rinsing and acid stripping of the reaction vessels.

Speciation calculations are one of the more common ways to describe a chemical system. Speciation diagrams is a convenient way to display such calculations and may also be the basis on which experiments in neighbouring fields of interest, such as sorption are based. In earlier days only very simple problems could be described, e.g. hydroxide species dominance diagrams versus pH. With the aid of computers, however, more complicated systems such as groundwater chemistry may be used. However, as the complexity increase, so does the effect of uncertainties. In this paper we focus on the effect uncertainties in stability constants may have on speciation calculations. The common belief is that the curves will be replaced by narrow bands, while the truth is far from that. In many cases one or several species cover the entire region between 0 and 100%.