A coupled hydro-chemical-mechanical constitutive law for the Belgian Eurobitum bituminized waste is being developed by the International Centre for Numerical Methods and Engineering (Polytechnical University of Cataluna, Spain) to contribute to the study of the compatibility of Eurobitum with Boom Clay as a geological disposal environment. A large experimental programme is ongoing at SCK•CEN to support the development of a constitutive law for Eurobitum. Water uptake tests are being performed under different conditions to obtain insights in the parameters that influence the water uptake behaviour of Eurobitum. Furthermore, Environmental Scanning Electron Microscopy and microfocus X-ray Computer Tomography are used to characterize hydrated samples in order to improve the understanding of the water uptake processes. The salt content, the distribution of the salt crystals, and the membrane efficiency in the Eurobitum samples affect the swelling and pressure increase rate. High membrane efficiencies and a large amount of hygroscopic salts inside the Eurobitum samples result in very high pressures when almost no swelling is allowed. The pressure in small inactive samples with 28 wt.% NaNO 3 has risen to ~ 19 MPa after ~ 3 years of hydration in nearly constant volume conditions. Slower pressure increase rates are being measured for samples with 6, 12, 18, and 33 wt.% NaNO 3 .

In Belgium, compatibility studies are performed in view of the final disposal of nitrate-containing bituminised intermediate-level radioactive waste in Boom Clay, which is considered as a potential host formation. Due to the presence of large amounts of nitrate in the waste, a slow release of nitrate (and to a smaller extent also nitrite) into the Boom Clay is expected. Nitrate and/or nitrite reduction by redox-active components of the host rock may cause a geochemical perturbation of the clay and subsequently might affect its barrier function against the migration of radionuclides. This paper therefore addresses the possible oxidation of one of the main redox-active components of the Boom Clay, i.e. dissolved organic matter, by nitrate and nitrite. For this, abiotic and microbially mediated nitrate and nitrite reduction was studied during long-term batch tests (2-2.5 years) in Boom Clay pore water, containing 155 +/- 15 mg C/l present as humic and fulvic acids. Changes in the reducing capacity of the DOM due to oxidation were assessed successfully using two oxidants, namely ferricyanide and ferric citrate. The results of these experiments indicate that an abiotic reaction between DOM and nitrate does not occur or is characterised by very slow kinetics. On the other hand, a slow microbial nitrate reduction to nitrite was observed and the associated oxidation of DOM was confirmed by a decrease in the (partial) reducing capacity of DOM for ferric citrate. In contrast to nitrate, nitrite was shown to oxidise DOM both abiotically and mediated by microbes through (chemo) denitrification, although these reactions also seem to occur only at a rather slow rate. No significant change in the maximally obtainable reducing capacity of DOM (using ferricyanide) was detected during any of the observed reactions, suggesting that the impact of such a slow heterotrophic nitrate reduction is very limited. (C) 2016 Elsevier Ltd. All rights reserved.

Understanding polonium evaporation from lead-bismuth eutectic (LBE) is required for the design of nuclear installations that use liquid LBE as coolant or spallation target. In the present study we measured the time-dependent release of polonium from LBE samples in Ar/5 %H 2 and Ar between room temperature and 500 °C. Our experiments revealed that the majority of polonium in the samples evaporated according to established temperature correlations for the Henry constant of polonium in LBE. However a small fraction of polonium in the LBE behaved differently, causing a relatively large but transient polonium release at the start of evaporation experiments. We showed that this volatile fraction of polonium was located near the sample surface and was formed after prolonged exposure of the samples to air at room temperature. We speculate that the peculiar evaporation behavior of this surface polonium is caused by enrichment and association with an oxide layer.

Potentiometric oxygen sensors integrated with LSM (strontium-doped lanthanum manganite)-GDC (gadolinium-doped ceria) composite electrode have been developed for use in liquid LBE at low temperatures. The performance of these sensors has been evaluated in oxygen saturated LBE in the temperature range of 200–400°C. Their performance was compared with that for platinum electrode and Bi/Bi2O3 electrode. The sensor with LSM-GDC composite electrode performed well down to 200°C by using a voltmeter with high input resistance (>10GΩ), while those with platinum electrode and Bi/Bi2O3 electrode showed significant deviations at 200°C.

The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at the Belgian Nuclear Research Center SCK.CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluna, Spain).In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO3 leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography (mu CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity.When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO3 solution. After about four years of hydration in nearly constant volume water uptake tests, pressures pp to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1-2 mm were hydrated (as derived from mu CT and ESEM analyses), and only about 10-20% of the initial NaNO3 content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO3 leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is-limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images.The experimental results of pressure increase and NaNO3 leaching, as well as observations on mu CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO3 concentration in hydrated BW after about four years), were reproduced rather successfully. by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days (similar to 27 years) the pressure would have decreased to a value of similar to 2 MPa. (C) 2012 Elsevier B.V. All rights reserved.

The behavior of Eurobitum bituminized radioactive waste under geological disposal conditions is studied in water uptake tests at the Belgian Nuclear Research Centre SCK•CEN to assess the feasibility of geological disposal for the long-term management of this waste. The hydro-mechanical behavior of this waste is affected by the continuous evolution of the rheological properties of bitumen due to radio-oxidation (i.e. ageing). The effect of the bitumen ageing degree on the kinetics of the water uptake, swelling and NaNO3 leaching is investigated in water uptake tests with ~30 years old radioactive samples and inactive samples that were artificially aged. The first results of swelling and NaNO3 leaching of (i) radioactive samples that have been hydrated for more than 2 years at a constant total stress of 2.2 MPa, and (ii) a thermally aged sample that has been hydrated for ~1.5 years under nearly zero effective stress conditions, revealed lower swelling and higher leach rates for these samples compared to non-aged samples. The effect of ageing on the osmotic efficiency of bitumen as a semi-permeable membrane is less pronounced when swelling of the samples is limited, and changes in time, probably because of the formation of low porosity layers, which seems to mask the difference in bitumen membrane efficiency of aged and non-aged bituminized waste.

The operating temperature of electrochemical oxygen sensors can likely be lowered by reducing the solid electrolyte resistance. Most often, these sensors use yttria partially stabilized zirconia (e.g. (Y2O3)(0.05)(ZrO2)(0.95), (5-YSZ)) as solid electrolyte. In this paper, we discuss the use of better conducting ceramics than yttria partially stabilized zirconia, as solid electrolytes for oxygen sensors that can be applied in lead-bismuth eutectic (LBE) cooled nuclear reactors. Two stabilized zirconia ceramics ((Y2O3)(0.08)(ZrO2)(0.92), (8-YSZ): (Sc2O3)(0.1)(CeO2)(0.01)(ZrO2)(0.89)) are investigated as well as a hypostoichiometric perovskite-type La0.8Sr0.2Ga0.8Mg0.2O3-6. The results of microstructural analyses, thermochemical stability tests in LBE (at 360 degrees C), as well as mechanical tests and four-probe d.c. conductivity measurements (at 300-800 degrees C) are discussed and compared with the results that were obtained for a commercially available 5-YSZ (Friatec AG, Germany)(1). Of the three studied ceramics, 8-YSZ was identified as the most promising solid electrolyte to reduce the operating temperature of electrochemical oxygen sensors. (C) 2012 Elsevier B.V. All rights reserved.

Laboratory water uptake tests are performed at the Belgian Nuclear Research Centre SCK•CEN to obtain insight into the hydromechanical behavior of Eurobitum bituminized radioactive waste under geological disposal conditions. Small nonradioactive and radioactive Eurobitum samples are hydrated in restricted swelling conditions (i.e., nearly constant volume conditions and constant stress conditions). Microfocus X-ray computer tomography (μCT) proves to be a very suitable technique to follow up the ingress of water in the samples. μCT analyses demonstrate that, under the studied hydration conditions, the water uptake by Eurobitum samples is a diffusion controlled process. A characterization of the partially leached samples with environmental scanning electron microscopy (ESEM) shows that the hydration of salt crystals and the subsequent dilution of the salt solution result in an increase in pore size that is limited to a few tens of μm in restricted swelling conditions. The μCT and ESEM analyses allow improvement in the understanding of water uptake by Eurobitum in restricted swelling conditions. In this article we discuss the μCT and ESEM analyses of nonradioactive Eurobitum samples that were hydrated for 2 to 4 years at a constant stress of 1, 22, 33, and 44 bar or in nearly constant volume conditions.

Several important technological and economic trends are shaping the research on non-destructive testing techniques. They include increasing computerisation and automation, fusion of different NDT methods, new market expansions, use of the techniques as a process control tool, and a proliferation of merges, consolidations and joint ventures. Other important factors such as the development of new materials, the safety requirements in the civilian aerospace and the automotive sector, and awareness of plant maintenance have strongly increased the purchases of NDT equipment and services. Advanced computer technology is also enabling end users to quantitatively size flaws to better estimate the danger posed by such flaws. Rather than waiting to be forced to adopt non-destructive inspection techniques in order to meet safety standards, end users are willingly utilising these more efficient methods as a cost-saving and quality improvement measure. X-ray computed tomography (XCT) is also a NDT product of these ongoing developments. In the last two decades microfocus X-ray (μCT) has become a very important tool for doctors, material scientists, geologists, biologists, civil engineers, bio-engineers, dentists, etc., all dealing with materials of which the fine internal structure or the changes within the material are of outmost importance to understand the behaviour of the material or to have insights in the processes going on. μCT is now well accepted in those disciplines as well as submicron or nanotomography facilities. This keynote paper addresses the μand nanoCTbased research results linked to the activities of the research group ‘Materials Performance and Non-Destructive Testing’ of the Department of Metallurgy and Materials Engineering (MTM) in collaboration with other research groups of the KU Leuven and the SCK•CEN laboratory. The goal is to present a wide variety of application fields and to show how μand nanoCT can be applied as an NDT technique for quality control, the study of the material behaviour and its functional properties under specified environmental conditions, and production and material optimization.

This paper presents a coupled Chemo-Hydro-Mechanical (CHM) analysis of the behaviour of leached Bituminized Waste materials (BW). Under geological disposal conditions the main factor that affects the long-term behaviour of this kind of materials is water uptake. First, the long-term behavior of BW in contact with water has been studied. A formulation has been proposed for the analysis of deformation induced by dissolution of salts in porous media in contact with water. The equations include the effect of coupled transport phenomena and the formulation has been included as an extension in the coupled THM program CODE_BRIGHT. The impact of osmotic forces on the swelling of the material has been investigated by simulating water uptake swelling tests under confined conditions. The numerical analysis has proven to be able to furnish a satisfactory representation of the main observed patterns of the behaviour. A sensitivity analysis has also been carried out to examine the effect of various key parameters.

In Belgium, Boom Clay is studied as a reference host rock for the geological disposal of high-level and intermediate-level radioactive waste. Compatibility studies at the SCK•CEN aim at investigating a perturbation of the capacity of Boom Clay to retard the migration of radionuclides to the biosphere, after disposal of Eurobitum bituminized radioactive waste in the clay (Valcke et al., 2009, Aertsens et al., 2009, Bleyen et al., 2010).One of the geo-chemical perturbations is the possible oxidation of Boom Clay by the large amounts of nitrate that will be released by Eurobitum. A more oxidised Boom Clay could have a lower reducing capacity towards redox sensitive radionuclides, possibly enhancing their migration. As the conditions in the Boom Clay formation around a disposal gallery for Eurobitum are far from optimal for the growth of prokaryotes (limited space in the far-field, high pH in the near-field, gamma radiation by the waste during the first ∼300years (effect limited to the primary and secondary waste package)), the impact of microbially mediated reduction of nitrate and nitrite is unclear. Therefore, batch tests are performed at the SCK•CEN to study whether nitrate and nitrite can directly oxidise the main redoxactive components of Boom Clay (dissolved organic matter, kerogen, pyrite) without the mediation of prokaryotes.In a first series of batch tests, which are reported in this paper, the activity of denitrifying and nitrate reducing prokaryotes was inhibited by the addition of NaN3. NaN3 revealed to be an efficient inhibitor for these prokaryotes without affecting considerably the geochemistry of Boom Clay and/or Boom Clay pore water. Neither in batch tests with the Boom Clay slurries (with NaNO3 (0.1 and 1M) or NaNO2 (0.1M)) and with Boom Clay water (with 0.05 and 0.2M NaNO3) a pure chemical nitrate or nitrite reduction was observed after respectively 3, 7 and 17weeks and 1year (Boom Clay slurries) and about 2years (Boom Clay water). Furthermore, batch tests in which bacterial activity was allowed, demonstrated that the Boom Clay natural organic matter is a poor carbon source for (denitrifying and nitrate reducing) prokaryotes.

A laboratory percolation experiment was performed to study the effect of a NaNO3 plume on the Boom Clay. In this experiment, Boom Clay cores were consecutively percolated with Boom Clay pore water and Boom Clay pore water to which NaNO3 was added. The concentration of NaNO3 in the pore water was increased stepwise (0.1, 0.5, and 1 M NaNO3). The concentrations of Na, K, Ca, Mg and Sr in the eluted water were measured. After every switch of the NaNO3 concentration, the concentration profiles of K, Ca, Mg, and Sr showed a sharp rise, followed by a slow decrease. It was hypothesised that the cation elution curves are mainly determined by cation exchange processes.Reactive coupled transport modelling with the PHREEQC-2 code was used to describe the experimentally observed elution curves for the cations. Solute transport and water-clay interaction mechanisms, namely cation exchange, were accounted for in the model. Cation exchange parameters (cation exchange capacity and selectivity coefficients) previously determined on non-perturbed Boom Clay (De Craen et al., 2004) were used. A sensitivity analysis was performed to assess the influence of these parameter values on the goodness of the model to describe the experimental data. The model could fairly well describe the experimentally observed cation concentrations in the eluted water, confirming that cation exchange is indeed the dominant mechanism regulating the cation elution in the percolation experiments. (C) 2011 Elsevier Ltd. All rights reserved.

In geological disposal conditions, contact of Eurobitum bituminized radioactive waste, which contains high amounts of the hygroscopic and highly soluble NaNO3, with groundwater will result in water uptake and swelling of the waste, and in subsequent leaching of the embedded NaNO3 and radionuclides. The swelling of and the NaNO3 leaching from non-radioactive Eurobitum samples, comprised between two stainless steel filters and in contact with 0.1M KOH, was studied in restricted (semi-confined) swelling conditions, i.e. under a constant total stress, or counterpressure, of 2.2, 3.3, or 4.4MPa (i.e. oedometer conditions). Four tests were stopped after hydration times between 800 and 1500days, and the samples were analyzed by micro-focus X-ray Computer Tomography (μCT) and by Environmental Scanning Electron Microscopy (ESEM). The complete set of data enabled a consistent interpretation of the observations and lead to an improved understanding of the phenomenology of the water uptake, swelling, and NaNO3 leaching in restricted swelling conditions. Under the studied conditions, the bituminous matrix surrounding the NaNO3 crystals and pores with NaNO3 solution behaved as a highly efficient semi-permeable membrane, i.e. osmotic processes occurred. In the main part of the leached layers, a high average NaNO3 concentration and related to this a high osmotic pressure prevailed, explaining why in the studied range the swelling was not measurably affected by the counterpressure. At the interface with the stainless steel filters, a low permeable re-compressed bitumen layer was formed, contributing to the slow release of NaNO3 compared to the water uptake rate. A fully coupled Chemo-Hydro-Mechanical (CHM) constitutive model has been developed that integrates the key processes involved and that reproduces satisfactorily the results; this is presented in another work. Combination of the experimental and the modelling study allow to conclude that under semi-confined conditions the swelling of the bituminized waste, and its evolution with time, is the result of several transient processes (salts dissolution, diffusion of salts and water, advection, creep, involving a low permeability material with evolving thickness and properties) that moreover are non-linear and strongly coupled.

This paper presents a theoretical and experimental work aiming at understanding the mechanical behaviour of Bituminized Waste Product (BWP). This material is considered for this purpose as a mixture of bitumen and crystals of sodium nitrate. For BWP, both bitumen and crystals contribute to the creep deformations. In this study, an attempt is made to develop an elasto-viscoplastic model that describes the creep behaviour of BWP considering the constituents' creep behaviour.An experimental program has been set up to get insight in the material response. The elasto-viscoplastic constitutive model has been implemented into a finite element program. The modelling results have been compared with the experimental data. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

AbstractIn Belgium, Eurobitum intermediate-level long-lived bituminized radioactive waste containing large amounts of NaNO3, which is a hygroscopic and soluble salt, is to be disposed of in an underground repository in a geologically stable clay formation. The Boom Clay is studied as a potential host formation because of its favourable properties to limit and delay the migration of the leached radionuclides and other contaminants (heavy metals, NaNO3, organic molecules) to the biosphere. The emplacement of the bituminized waste will induce multiple processes that could have a significant effect on the key properties of the clay. Because several of these processes are interdependent, the study of the compatibility of Eurobitum with geological disposal is complex. To structure the research and to identify possible knowledge gaps, the Belgian Radioactive Waste Management Agency ONDRAF/NIRAS developed a new methodology based on safety functions and safety statements. In this paper, this methodology is briefly explained, with reference to the disposal of Eurobitum. Experimental results obtained at the Belgian Nuclear Research Centre SCK•CEN are presented and discussed in the light of the safety functions and safety statements approach. The importance of the interdependence of the processes is highlighted. Special attention is given to the evolution of the disposal design as a result of the improved understanding of key processes.

According to the present Belgian radioactive waste management program, Eurobitum bituminised radioactive waste will be disposed of in a geologically stable underground clay formation. The Boom Clay is studied as a potential host formation because of its low diffusion and high retention properties towards radionuclides. The presence of the radioactive waste should not disturb these properties. Due to the presence of hygroscopic salts (25 to 30 weight% NaNO3), Eurobitum will take up pore water which will result in a swelling and possibly in a very high swelling pressure. First scoping calculations suggest that the swelling pressure exerted to Boom Clay should remain below 7 to 8 MPa to avoid the formation of fractures. If the bitumen in EUROBITUM behaved like a perfect semi-permeable membrane and if no swelling were allowed after the dissolution of NaNO3 into a saturated solution of 10.8 M, osmotic pressures of ∼50 MPa could be attained. To better understand the interaction between the swelling Eurobitum and the host formation, coupled hydro-chemical-mechanical constitutive laws for Eurobitum have to be developed. To this purpose, water uptake tests under constant volume (‘confined’) and constant stress (‘semi-confined’) conditions are being performed. After ∼2 years of hydration of small inactive Eurobitum samples in constant volume conditions, the swelling pressure has raised to ∼12 MPa. The volume of samples that can swell against counter pressures of 2.2, 3.3, or 4.4 MPa (constant stress tests) increased with ∼5 to 11 volume%, independently of the applied counter pressure. Approximately 10 weight% of the initial NaNO3 content has been leached.

R306465 is a novel hydroxamate-based histone deacetylase (HDAC) inhibitor with broad-spectrum antitumour activity against solid and haematological malignancies in preclinical models. R306465 was found to be a potent inhibitor of HDAC1 and -8 (class I) in vitro. It rapidly induced histone 3 (H3) acetylation and strongly upregulated expression of p21waf1,cip1, a downstream component of HDAC1 signalling, in A2780 ovarian carcinoma cells. R306465 showed class I HDAC isotype selectivity as evidenced by poor inhibition of HDAC6 (class IIb) confirmed by the absence of downregulation of Hsp90 chaperone c-raf protein expression and tubulin acetylation. This distinguished it from other HDAC inhibitors currently in clinical development that were either more potent towards HDAC6 (e.g. vorinostat) or had a broader HDAC inhibition spectrum (e.g. panobinostat). R306465 potently inhibited cell proliferation of all main solid tumour indications, including ovarian, lung, colon, breast and prostate cancer cell lines, with IC50 values ranging from 30 to 300 nM. Haematological cell lines, including acute lymphoblastic leukaemia, acute myeloid leukaemia, chronic lymphoblastic leukaemia, chronic myeloid leukaemia, lymphoma and myeloma, were potently inhibited at a similar concentration range. R306465 induced apoptosis and inhibited angiogenesis in cell-based assays and had potent oral in vivo antitumoral activity in xenograft models. Once-daily oral administration of R306465 at well-tolerated doses inhibited the growth of A2780 ovarian, H460 lung and HCT116 colon carcinomas in immunodeficient mice. The high activity of R306465 in cell-based assays and in vivo after oral administration makes R306465 a promising novel antitumoral agent with potential applicability in a broad spectrum of human malignancies.

A series of pyrimidyl-5-hydroxamic acids was prepared for evaluation as inhibitors of histone deacetylase (HDAC). Amino-2-pyrimidinyl can be used as a linker to provide HDAC inhibitors of good enzymatic potency.