A luminescence line-narrowing spectroscopic study of the uranium(VI) interaction with cementitious materials and titanium dioxide

Non-selective luminescence spectroscopy and luminescence line-narrowing spectroscopy were used to study the retention of UO22+ on titanium dioxide (TiO2), synthetic calcium silicate hydrate (C-S-H) phases and hardened cement paste (HCP). Non-selective luminescence spectra showed strong inhomogeneous line broadening resulting from a strongly disordered UO22+ bonding environment. This problem was largely overcome by using luminescence line-narrowing spectroscopy. This technique allowed unambiguous identification of three different types of UO22+ sorbed species on C-S-H phases and HCP. Comparison with spectra of UO22+ sorbed onto TiO2 further allowed these species to be assigned to a surface complex, an incorporated species and an uranate-like surface precipitate. This information provides the basis for mechanistic models describing the UO22+ sorption onto C-S-H phases and HCP and the assessment of the mobility of this radionuclide in a deep geological repository for low and intermediate level radioactive waste (L/ILW) as this kind of waste is often solidified with cement prior to storage.Swiss National Cooperative for the Disposal of Radioactive Wast

The AllWISE Motion Survey and the Quest for Cold Subdwarfs

The AllWISE processing pipeline has measured motions for all objects detected on Wide-field Infrared Survey Explorer (WISE) images taken between 2010 January and 2011 February. In this paper, we discuss new capabilities made to the software pipeline in order to make motion measurements possible, and we characterize the resulting data products for use by future researchers. Using a stringent set of selection criteria, we find 22,445 objects that have significant AllWISE motions, of which 3525 have motions that can be independently confirmed from earlier Two Micron All Sky Survey (2MASS) images, yet lack any published motions in SIMBAD. Another 58 sources lack 2MASS counterparts and are presented as motion candidates only. Limited spectroscopic follow-up of this list has already revealed eight new L subdwarfs. These may provide the first hints of a "subdwarf gap" at mid-L types that would indicate the break between the stellar and substellar populations at low metallicities (i.e., old ages). Another object in the motion list—WISEA J154045.67–510139.3—is a bright (J ≈ 9 mag) object of type M6; both the spectrophotometric distance and a crude preliminary parallax place it ~6 pc from the Sun. We also compare our list of motion objects to the recently published list of 762 WISE motion objects from Luhman. While these first large motion studies with WISE data have been very successful in revealing previously overlooked nearby dwarfs, both studies missed objects that the other found, demonstrating that many other nearby objects likely await discovery in the AllWISE data products

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Influence de la température sur la rétention du sélénite par une pâte de ciment altérée et par ses phases pures constitutives

In the French design of a deep repository for radioactive waste, cementitious materials willundergo a constraint in temperature, due to cement hydration exothermic reactions and tothe heat generation of radioactive waste. Such temperature changes (to a maximum value of60-70°C) could affect the cement paste mineralogy and could therefore impact radionuclidesretention properties. Selenium, whose the radioisotope $^{79}$Se (T$_{1/2}$ = 6,5.10$^5$ years) is a fissionproduct, has been chosen for the retention study because of its sensitivity in the changes ofthe mineralogical composition of the cement pastes. The main objective was to study theeffect of temperature on selenite sorption with thermally altered cement pastes (CEM I) andrelative individual cement phases (portlandite, C-S-H, ettringite and hydrogarnet.With increasing temperature, we observed: 1) modifications of the mineralogical compositionof altered cement pastes, which seem irreversible and modifications of the ionic activityproducts of pure cement phases. These changes have been predicted with a thermodynamiccalculation; 2) a decrease of selenite retention affinity for all studied solid phases. This effectcan not be explained only by mineralogical modification, but also by the modification ofequilibrium solution composition (particularly with calcium and sulphate concentrations insolution).Modelling attempts proposed in this study didn’t achieve to build a predictive model but mustbe considered as a first step in the right direction to obtain a mechanistic model. Describingselenite sorption onto cementitious phases as a function of temperature needs moreinformation in order to complete the thermodynamic database for cement materials (Log_Kand ΔH°), to characterize surface sites of the pure cementitious phases and determine theircomplexation constants as a function of temperature. Finally, it is necessary to determine thecomplexation constants of competitive and complexe ions (respectively sulfate and calcium).Les études menées dans le cadre du projet français de stockage de déchets radioactifs enformation géologique profonde montrent que les matériaux cimentaires devraient subir unecontrainte en température, due à l’échange thermique entre le colis de déchet radioactif et lebéton, et due aux réactions exothermiques d’hydratation des phases anhydres du ciment.Cette augmentation de température (jusqu’à maximum 60-70°C) peut modifier le cortègeminéralogique des pâtes de ciment et influencer leurs propriétés de rétention desradionucléides. Le sélénium, dont le radioisotope $^{79}Se$ (T$_{1/2}$ = 6,5.10$^5$ ans) est un produit defission, a été choisi pour cette étude de rétention en raison de sa sensibilité auxchangements de la composition minéralogique des pâtes de ciment. L’objectif majeur de cetravail a été d’étudier l’influence de la température sur la rétention de sélénite par une pâtede ciment altérée de type CEM I et par ses phases pures constitutives (portlandite, C-S-H,ettringite et hydrogrenat.Avec l’augmentation de la température, nous avons observé : 1) des changements decomposition minéralogique des pâtes de ciment qui semblent irréversibles et desmodifications des produits de solubilités des phases pures. Ces changements ont pu êtreprédits à partir de calculs thermodynamiques ; 2) une diminution de l’affinité de sélénite quelque soit le solide étudié. Ces changements ne peuvent pas être expliqués à partir desmodifications minéralogiques seules et semblent être corrélés à l’évolution de la chimie ensolution, en particulier à la présence de calcium et sulfate en solution.Les essais de modélisation proposés ne permettent pas d’obtenir des calculs prédictifs dequalité suffisante, mais doivent être considérés comme une première étape vers lamodélisation mécanistique de ces systèmes complexes. Ainsi, construire un modèle prédictifde la rétention de sélénite par les pâtes de ciment en fonction de la température nécessitedes données supplémentaires afin de compléter la base de données thermodynamiques desphases cimentaires pures (Log_K et ΔH°), de caractériser les sites de surfaces de cesphases pures et déterminer leurs constantes de complexation en fonction de la température.Enfin, il conviendra aussi de déterminer les constantes de complexation des ionscompétiteurs (les sulfates) et/ou des ions complexants (le calcium)

Influence de la température sur la rétention du sélénite par une pâte de ciment altérée et par ses phases pures constitutives

Cette étude s inscrit dans le cadre du projet français de stockage de déchets radioactifs en formation géologique profonde (loi du 30/12/91). Lors de la mise en place des colis de déchets, les matériaux cimentaires (béton, mortier), envisagés par exemple, comme sur-conteneurs pour les déchets B, subiront une augmentation de température (jusqu à 60-70C), qui peut modifier leur cortège minéralogique et influencer leurs propriétés de rétention vis-à-vis des radionucléides. Le sélénium (79Se, T1/2 = 6,5.105 ans), produit de fission présent dans ces colis, a été choisi pour cette étude de rétention en raison de sa sensibilité aux changements minéralogiques des pâtes cimentaires. L objectif majeur a été d étudier l influence de la température sur la rétention de Se(IV) par une pâte de ciment altérée de type CEM I et par ses phases pures constitutives (portlandite, C-S-H, ettringite et hydrogrenat). Avec l augmentation de la température, nous avons observé : 1) des changements de composition minéralogique des pâtes de ciment et des modifications des produits de solubilités des phases pures. Ces changements ont pu être prédits à partir de calculs thermodynamiques 2) une diminution de l affinité du sélénite quel que soit le solide étudié. Ces changements ne peuvent pas être uniquement expliqués par les modifications minéralogiques et semblent être corrélés à l évolution de la chimie en solution, en particulier à la présence de calcium et sulfate en solution. Les essais de modélisation proposés ne permettent pas d obtenir des calculs prédictifs de qualité suffisante, mais doivent être considérés comme une étape vers la modélisation mécanistique de ces systèmes complexes.In the French design of a deep repository for radioactive waste, cementitious materials are considered as container or buffer and backfill materials in the engineered barrier system. The temperature would temporally increase from ambient to a maximum value of 70C, due to cement hydration exothermic reactions and to the heat generation of radioactive waste. Such temperature changes could affect the cement paste mineralogy and could therefore impact radionuclides retention properties. Selenium has been chosen for the retention study, since the radioisotope 79Se (T1/2 = 6.5 105 years) contributes to the long term hazard of radioactive waste disposal. The main objective is to study the effect of temperature on selenite sorption with thermally altered cement pastes (CEM I) and relative individual cement phases (portlandite, C-S-H, ettringite and hydrogarnet). Results show that increasing of temperature affects: 1) the mineralogical composition of thermally altered cement pastes and the ionic activity products of pure cement phases. This effect has been predicted with a thermodynamic calculation 2) the sorption properties of selenite affinity. Decreasing Rd values with temperature can not be explained only by mineralogical modification, but also by the modification of equilibrium solution composition (particularly with calcium and sulphate concentrations). The construction of a predictive and mechanistic model to describe Se(IV) sorption onto cementitious phases as a function of temperature was not possible because of a lack of sufficient data, but the present work can be considered as a step in this direction.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

INTERACTIONS AND MIGRATION OF ORGANICS (EDTA & PHTHALATE) IN CEMENT BASED MATERIALS IN WEATHERING STATE II AND IV

International audienc

Uranium(VI) sorption onto hardened cement paste under high saline and alkaline conditions

International audienceEvaluation of the mobility behaviour of radionuclides under highly saline and alkaline conditions is a major concern for the performance assessment of radioactive waste disposal. The aim of this study was to determine the effect of up to 2.8 mol/kgsolution content of NaNO3, on the solubility and the retention of U(VI) at 22 °C onto a hardened cement paste (HCP) prepared from ordinary Portland cement (CEM I). To avoid the interference of the high salt concentration and ionic strength,and because of the expected low solubility of uranium under such alkaline conditions, time-resolved laser fluorescence spectroscopy (TRLFS) was selected to accurately measure U(VI) concentration in solution using the standard addition method in 85% H3PO4. This allows both limiting the dilution and matrix effects and determining the resulting [U(VI)] in solution with acceptable precision for the distribution factor (Rd) in both sorption and desorption experiments. The operational solubilitylimit measured at high ionic strength lowered by a factor of three compared to the reference cementitious condition, and its Rd values decreased by a factor ca. four. The sorption of U(VI) appears to be reversible under these conditions

MULTISCALE STUDY OF CHLORIDE MIGRATION IN CONCRETE

International audienceConcrete plays an essential role in the management and disposal of radioactive waste. Its durability, strength and radiation resistance make it an appropriate material for the construction of containers and barriers to contain and isolate radioactive waste for long periods of time. In this context, the diffusion of chlorides into concrete can significantly affect its durability and service life. Chlorides can penetrate the concrete through pores and cracks, causing corrosion of the steel reinforcement, which can ultimately lead to structural damage and failure. This study is part of a PhD project investigating the effect of aggregates on the transport properties of concrete. Due to the high heterogeneity of concrete, a multi-scale study is carried out by sieving the fresh concrete mix to separate each phase: concrete, mortar and cement paste. The studied concrete is a mature CEM I concrete with a water-cement ratio equal to 0.43 cured in 98% HR during two years before migration experiment. The use of 36Cl radioactive tracer has been chosen to accurately measure the diffusion profile at low concentrations, rather than traditional methods such as ion chromatography technique which requires higher concentrations level

Effects of organic degradation products on the migration behaviour of radionuclides in cementitious materials

International audienceThe impact of phthalates, which might be present in a cementitious repository as degradation products of superplasticisers or PVC additives, on the migration behaviour of An(III)/Ln(III) was investigated in batch sorption experiments on hardenedcement paste. In the absence of organics, An(III)/Ln(III) sorb strongly on HCP with distribution ratios, Rd, of 10^5 to 10^6 L/kg. Above a no-effect level of ~ 1E–03 mol/L phthalate, a distinct decrease of the An(III)/Ln(III) sorption was observed withsorption reduction factors (i.e., the ratio between the Rd values without and with organic ligand) of 100 to 1000 at phthalate concentrations of 1E–01 mol/L. This sorption reduction is attributed to the effect of Ca complexation with phthalate on thestability of calcium silicate hydrate (C–S–H) phases as main sorbing phase. These results and ongoing diffusion experiments indicate an increase in the mobility of An(III)/Ln(III) in cementitious barriers with increasing phthalate concentrations

INTERACTIONS OF ORGANIC MOLECULES AND URANIUM WITH CALCIUM ALUMINUM SILICATE HYDRATES

International audienceNuclear energy accounted for 10.3% of global electricity production in 2019 and is being considered by some countries as a low-carbon technology for mitigating climate change [1]. Deep geological repositories (DGR) are the most accepted way to safely isolate radioactive waste. In this concept, adsorption is one of the main processes expected to limit transport of dissolved radionuclides. Cements are extensively used as construction and encapsulation materials in repositories. One of the main hydration products of cement is calcium-silicate-hydrate (C-S-H). When fly ash is added to the cement, calcium-aluminate-silicate-hydrate (C-A-S-H) phases can be formed with different structures to C-S-H as well as higher chain lengths [2]. Despite their expected ubiquity in a DGR, the sorption of radionuclides on C-A-S-H phases have received minimal attention. As well as radionuclides, organic materials are also expected to comprise a portion of disposed material. These take on relevance in the context of nuclear waste management, as they can affect both the solubility and sorption behavior of radionuclides. The research described in this work investigates the interaction of three organic molecules (adipate, phthalate, and isosaccharinate, ISA) and uranium with C-A-S-H