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Un important programme de recherches, appele « Generation IV », est actuellement developpe au niveau international pour preparer les reacteurs du futur et leurs « cycle de combustible ». Son objectif est de satisfaire les besoins croissants en energie electrique dans le cadre d'un developpement durable. L'un des aspects majeurs de ce programme est la recherche et le developpement de nouveaux materiaux nucleaires fissiles/fertiles. Malheureusement, on s'apercoit aujourd'hui que, pour de nombreux composes candidats pour developper ces materiaux, il n'existe pas de donnees radiotoxicologiques permettant au medecin du travail d'evaluer le risque reel en cas de contamination et de prescrire un traitement de decontamination adapte. Il conviendrait donc de relancer d'urgence les etudes de poste ou sont, ou bien seront, mis en œuvre ces composes ou materiaux. L'experience passee a montre que la prevision en matiere de radioprotection etait difficile et qu'une validation experimentale du comportement des elements lourds radiotoxiques ou toxiques in vitro et in vivo etait necessaire.

A method is proposed where the values of entropy change upon formation of LnL (H2O)nand AnL (H2O)nlanthanide and actinide complexes in aqueous solutions are used to determine the coordination numbers of Ln3+and An3+and the number of coordinated water molecules in these complexes.

In the back-end of the nuclear fuel cycle, liquid–liquid extraction is the selected separation method. For an improved design of new extracting agent, the knowledge of the coordination polyhedra of the metal ions is important. In this paper, we investigated the coordination sphere of a series of uranyl complexes with selected organophosphorus extracting molecules: UO2(NO3)2L2 (with L=tri-iso-butylphosphate, tri-n-butylphosphate, trimethylphosphate and triphenylphosphate) using X-ray absorption spectroscopy. FEFF7 calculations of the EXAFS spectra corresponding to the model compound UO2(NO3)2(TiBP)2 (with TiBP=tri-iso-butylphosphate) for which the crystal structure is known led to a multiple scattering approach of the data fitting. EXAFS results show subtle U–O(P) bond distance differences between the different complexes that are discussed in terms of both electronic and steric effects of L. These results are discussed with regards to the extraction ability of L. In the same time, exploratory work has been attempted in order to evaluate U–O–P bond angle variations as a function of L using multiple photon-scattering paths. Satisfactory values have been obtained compared to the crystallographic data.

For the design of new liquid-liquid extracting agents, which may or may not coordinate with elements to be separated, knowledge of the coordination polyhedra of the metal ions is important. In this paper, this information was obtained for the solvate UO2(NO3)2(TBP)2] (with TBP = tributylphosphate) using X-ray absorption spectroscopy. It includes the analysis and ab initio calculation of the EXAFS and XANES spectra corresponding to the model compound UO2(NO3)2(TIBP)2] (with TIBP = tri-iso-butylphosphate) for which the crystal structure is known. The EXAFS results show little differences between the coordination polyhedra of the uranium ions engaged in both compounds, at low (77 K) or room (295 K) temperatures. The uranium eight-coordination polyhedron is composed of two uranyl oxygens located at 1.76 A, four nitrate (bidentate) oxygens located at 2.51 A and two phosphate oxygens located at 2.42 A. Finally, investigation of the XANES spectra fully confirmed these results.

The advantages of the capillary electrophoresis method, known to be highly selective, have been tested on some standard latex colloids and nanoparticles of thorium phosphate, investigated separately or in mixtures. The results have been compared to those obtained by laser Doppler velocimetry. Both methods appear as complementary: capillary electrophoresis is more efficient to point out very fine particles among others, but is more restricting about the supporting medium.

An evaluation of E° (3/2) redox potentials of lanthanides and actinides with fqd electronic configuration is achieved. It takes into account the known equations already given for elements with fq electronic configuration and a proposed correction due to the fqd electronic stabilization.

European construction raises at the great day, the theoretical faults of the traditional design of contemporary public sphere. In the light of investigation empirical, this text tries a conceptual definition of the three features characteristic of public space.

The paper deals with radiochemistry of tracer amounts of radionucli des with N=1 to 100 or several hundreds of species/cm3.

International audience; The mechanism of M(III) extraction (M = Am, Eu) using mixtures of purified Cyanex 301 with neutral O-bearing co-extractants is investigated from the standpoint of theoretical chemistry. The strong coordination of M(III) to soft donor S atoms of Cyanex 301 is shown to be caused by a covalent effect that is significantly greater for Am(III)─S than for Eu(III)─S bonds. The M(III) extractabilities are correlated with the calculated effective charge on O atom in neutral organophosphorous co-extractant molecules. Synergism is explained by the formation of mixed ligand complexes which changes the nature of the M─S bonds due to O → M electron density transfer. Co-extractants which are weak donors strengthen M─S bonds but strong donors weaken them. The 31P NMR chemical shifts of the neutral O-bearing organophosphorous co-extractants, which are correlated with the M(III) extractabilities, confirm the synergism mechanism. Shifts in charge transfer energy in UV-visible absorption spectra of Eu(III) synergistic mixed complexes compared with Eu(III)-Cyanex 301 complexes are related to the Eu–S distances in the extracted complexes. The Eu–S distances in the Eu(III) extracted complexes were also found to be related to the intensity of the synergistic effect and to the Am(III)/Eu(III) extraction selectivity.

International audience; The mechanism of the formation of a complex between several planar terdentate nitrogen ligands and trivalentlanthanides (Ln$^{3+}$) in mixed MeOH–H$_2$O solutions is studied and a model is proposed for the thermodynamicproperties of the complexation reactions. The objective is not to cover all aspects of complexation betweenLn$^{3+}$ and planar terdendate nitrogen ligands, but rather to provide insight into the factors that govern thecomplexation mechanism. It is shown that the complexation of Ln$^{3+}$ in solution with similar ligands does notfollow the classical trends in change of thermodynamic properties across the Ln series, which have long beenknown. Ab initio calculations show that the stability of complexes increases with the increasing electron donorability of the coordinating central nitrogen atom (N$_c$) of the ligand and the electron acceptor ability of thecoordinating lateral ones (N$_l$). The effect of covalence for the stability of complexes is analysed. The complexeswith high stability are characterised by distinct covalence of the bonds between Ln$^{3+}$ and the lateralcoordinating nitrogen atoms of the ligand. The thermodynamic properties of complexation of Ln$^{3+}$ with2,6-bis-(pyridin-2-yl)-4-amino-1,3,5-triazine (Adptz) and 2,6-bis-(1,2,4-triazin-yl)-pyridine (Btp) are compared.The central ring is negatively charged in the Adptz ligand, but positive in Btp. The strong donor–acceptorinteraction and the net covalence result in an enthalpy mechanism of complexation of Ln$^{3+}$ with Adptz. Owingto the repulsion between the cation and the central nitrogen atom in the [Ln(Btp)]$^{3+}_{solv}$ complexes, the cation ispushed away from the nitrogen cavity, the Ln–Nc interatomic distances become larger and the electron donorability of N$_c$ is weak. Entropy promotes the formation of the [Ln(Btp)]$^{3+}_{solv}$ complex.

The mechanism of synergistic selective extraction of Am(III) over Eu(III) from aqueous nitric acid solutions using di(chlorophenyl)dithiophosphinic acid [(Cl Phi)(2)PSSH] and neutral O-bearing organophosphorus co-extractants (B) has been investigated. (Cl Phi)(2)PSSH forms weaker complexes with Am(III) than R2PSSH (where R = alkyl group). However, the Am(III)/(Cl Phi)(2)PSSH complexes are stronger than the corresponding Eu(III)/(Cl Phi)(2)PSSH complexes, although the difference is not as large as in the case of the corresponding complexes formed with R2PSSH. The donor properties of co-extractants are also discussed. Chemical shifts in the P-31 NMR spectra of the organophosphorus co-extractants correlate qualitatively with the extractability of Am(III) and Eu(III) in (Cl Phi)(2)PSSH + B synergistic mixtures. The synergistic effect determines the selectivity not only qualitatively but also quantitatively. The high selectivity observed using tri-2-ethylhexyl phosphate (T2EHP) is caused by a synergistic bonding effect for the Am(III) complex and an antagonistic effect for Eu(III).A donor-acceptor mechanism is shown to promote Am(III) extraction for almost all B co-extractants. A contribution of entropy terms for extracted Eu(III) extraction is assumed to be significant. Interatomic distances REu-S in the Eu(III) complexes are calculated.The softness of S-bearing extractants XYPSSH (with X and Y = R, RO or ClC6H4) is discussed from the point of view of the effective charge carried by the S atoms. The hardness of Eu(III) and Am(III) is evaluated.

Recently [1] it was claimed that (i) the reaction of ThCl 4 with HN 3 in slightly acidic aqueous solution produces the aqueous ion of Th(III) according to the thermodynamically allowed reaction: Th 4+ + HN 3 → Th 3+ + 1.5N 2 + H + ; (ii) Th(III) was identified by its absorption (UV-vis. 200–1300 nm) and ESR spectra. This paper is aimed to prove that the aqueous ion Th 3+ (aq) is thermodynamically unstable and that the identification of Th(III) in the considered solutions ask for new experiments.

The problem of bond energies in the nitrato compounds of trivalent lanthanides, Ln, with malonamides, L, of the type: Ln(NO 3 ) 3 (H 2 O) m L and Ln(NO 3 ) 3 L 2 , (L=CH 2 (OCNR 1 R 2 ) 2 ) is approached through a semi-empirical theory connecting thermodynamic with structural properties (STT). Emphasis is given on the relation between bond energies and solvent extraction of complexes of Ln with L from nitric aqueous solutions. STT is presented and applied to nitrato compounds with R 1 =ethyl, R 2 =ethyl, R 1 =methyl, R 2 =cyclohexyl and R 1 =methyl, R 2 =phenyl. For the first time, the effect of the regular decrease of the bond energies Ln–O(nitrato) and Ln–O(L) with the increase of the volume of L is evidenced. The enthalpies of extraction of Ln by L from low nitric acid concentration are calculated. Finally, rules connecting the distribution coefficients D(Ln) in liquid–liquid extraction of Ln (III) by diamides is formulated. These rules appear as a useful guide to predict D(Ln) variation along the series.

The equilibrium between thorium orthophosphate (Th 3 (PO 4 ) 4 ), labelled with the radioactive thorium isotope 227 Th, and phosphate-containing solutions has been investigated as a function of pH and total concentration of phosphate groups (5 c PO4 −1 ). Since Th 3 (PO 4 ) 4 is a very insoluble compound, even in relatively concentrated phosphoric media, 227 Th has been detected in solutions near neutrality only for c PO4 > 0.1 mol 1 −1 . Under these conditions, the thorium concentration has been measured after ultrafiltration (cutting size of the species at 5 nm) by γ-ray spectroscopy in the range 10 −9 –10 −5 mol 1 −1 . The solubility curves, c Th vs . pH value at constant c PO4 and O 2 vs . c PO4 at constant pH, lead to the determination of the prevailing species in the solutions: at a pH of 6–7, [ThO(HPO 4 ) 3 (H 2 PO 4 )] 5- and [ThO(HPO 4 ) 3 (H 2 PO 4 ) 2 ] 6- are the presumed complex forms of thorium for 0.3 c PO4 −1 and 0.8 c PO4 −1 respectively.

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In this paper we define a digital document according to three levels of structure: its organization structure, its control structure and its interactivity structure. Whereas these three structures exist inherently in every document, they are redefined when dealing with digital documents, since they can be abstracted and formalised, and consequently manipulated. We show how these three structures are implemented within the SCENARI publishing chain, which provided us a framework of application in real project.

We have investigated the behaviour of109Cd, in two-phase systems: (HDEHP−C6 H6/ H3 PO4−HClO4−LiOH, μ=0.2), as a function of the independent equilibrium parameters which define the system: pH, equilibrium concentration of H3 PO4 and total concentration of HDEHP in the organic phase. The data have been interpreted in terms of the existence of phosphoric complexes characterized by their order 1 with regard to H3 PO4 and their charge z. The l and z. values are: 0

Resume Le comportement de l'americium de l'echelle des indicateurs aux quantites ponderables de matiere dans des milieux citriques de force ionique 0,1 a ete etudie par extraction par solvant et potentiometrie. Differents complexes ont ete mis en evidence et leurs constantes de formation ont ete determinees. Les caracteristiques spectroscopiques de certains complexes, notamment Am(cit) 2 3− et (Am(OH)(cit)) 2 2− , ont ete relevees et analysees. Des citrates cristallises d'americium ont ete prepares.

Irradiation of ThBr/sub 4/ single crystals by energetic electrons and ..cap alpha.. particles gives rise to an emission over a broad band at 405 nm. This emission has been stuied in terms of the nature and energy of both particles and with beam intensity. The radioluminescence conversion efficiency is about 6 +- 2 percent for electrons at 250 keV and 2 +- 1 percent for ..cap alpha.. particles at 5 MeV. ThBr/sub 4/ is as well as other ''phosphor''.

Experimental and computed data on the solubility of uranium (IV) oxide in water and aqueous solutions have been critically reviewed and the computed data from different sources compared. The computed solubility data differ by as much as seven orders of magnitude. It is thus concluded that the effect of the numerical value of the equilibrium constants invoked in the computation of the solubility values is crucial. Only limited confidence should be placed in computed predictions when the quality of the input data is not known.

We prepared ThBr4 on a large scale and grew a single crystal by the Bridgman method. The volume obtained is around few cubic centimeters. ThBr4 is fluorescent under UV (λ

Solvent extraction (150°C) of lanthanides with TTA dissolved in polyphenyl eutectic from a molten salt (LiNO3z.sbnd;KNO3) has been studied in closed systems as a function of CTTA, pNO2 and pO2. Distribution data and other measurements are consistent with mechanisms which go through dimerisation of TTA in the organic phase. Influence of the composition of gaseous phase could be quite important as shown on neodymium.

The optical spectra of U 4+ ion (5 f 2 ) at a site of D 2d symmetry were studied by different authors in various matrices as UCl 4 [1–5], ZrSiO 4 [6, 7]. HfSiO 4 [8], ThSiO 4 [8] and ThBr 4 [9, 4]. There also exist data on magnetic susceptibility of UCl 4 [10–13] and USiO 4 [14] but most results do not agree with those obtained from optical spectra. At this point, one can note the disparity between the previous results concerning UCl 4 , which was the most studied of all these crystals and mention the necessity of performing both optical and magnetic studies on single crystals of the same origin. A recent study of these issues leads to a better agreement [5, 15]. Therefore, it seems of interest of grow some of these crystals as single crystals and study again the optical spectra of U 4+ in the D 2d symmetry. This way we could compare the spectra to one another in order to assign the absorption and emission lines more accurately. So we grew single crystals of UCl 4 and ThCl 4 : U 4+ by the Bridgman method [16] and ThSiO 4 : U 4+ by the flux method following Chase and Osmer [17]. Then we recorded polarized spectra of U 4+ in ThCl 4 and ThSiO 4 (Fig. 1) and unpolarized spectra for UCl 4 (Fig. 2). In all these spectra the main features are quite similar but the more clear ones are obtained with ThSiO 4 :U 4+ . In fact, the U 4+ absorption bands in UCl 4 are very broad, probably due to the interaction between the U 4+ ions and in ThCl 4 : U 4+ they are affected by the incommensurate and modulated structure of the low temperature phase of ThCl 4 . This interesting last point needs more explanations. In ThCl 4 a phase transition occurs at 40 K and the dynamic of the structure alteration was studied in the isomorphic crystal ThBr 4 , mainly by neutron diffraction [18]. It was shown that the matrix loses its periodic structure in one direction (the z axis corresponding to the S 4 optical axis). The halide displacements are different in each until cell and can be described by a sinus function of the distance to the origin of the unic cell. This result in having the Th 4+ ion and therefore its substitute U 4+ in an affinity of D 2 symmetry sites and some of D 2d symmetry (each D 2 site being very close to the D 2d symmetry). This continuous modulation of the D 2 symmetry between two maximum distortions gives rise to special features which have not been seen up to now in any other optical spectra. The absorption and emission lines of U 4+ in ThCl 4 , rise and fall very steeply due to edge singularities which are connected by a continuum of lines corresponding to U 4+ in the intermediate D 2 symmetries [19–21] (Fig. 3). Selective excitation of the different sites produces fluorescence lines whose energy varies continuously between the system singularities (Fig. 4). Thus in ThCl 4 , The U 4+ doping ion acts as an indicator of the incommensurate structure of the low temperature phase. One question that arises then is: would a lanthanide give the same type of information? Though the phenomenon seems much smaller as one would expect with the 4f electrons which are more protected against the crystal field interaction, some special features were recorded in the spectra of Pr 3+ (4f 2 ) in ThCl 4 (Figs. 5, 6) and are under study [22]. In conclusion, ThSiO 4 :U 4+ spectra give the clearest set of data concerning U 4+ in the D 2d site symmetry. The spectra are well polarized with only two allowed dipolar electric transitions: Γ 4 → Γ 5 (σ polarization) and Γ 4 → Γ 2 (π polarization). So the results on ThSiO 4 :U 4+ appear as essential to improve the calculations of the usual spectroscopic parameters (the Slater's parameters F k , the spin-orbit constant ξ and the crystal field parameters B k q for the two other crystals ThCl 4 :U 4+ and UCl 4 . These calculations are underway.

Coherent values of s1, ΔH° and δS° for complexing of Maq3+ ions (M = Sm, Eu, Gd, Tb and Dy) by L− (L = Cl, Br, I, NO3, F) (μ = 1) have been obtained by solvent extraction method, using aqueous phases containing all the elements. ΔH° values vs Z, shows the “gadolinium break”.

ThBr4 and ThCl4 are new inorganic scintillators, We review their responses to gamma rays, protons, deutons, alpha particles and heavy ions. All calibrations are referred to an ? line provided by the self-induced ? spectrum. Some features like resolution are similar to those of other ionic scintillators but some differences such as relative scintillation efficiency, scintillation decay time and resistance to radiation damages are pointed out in comparison with NaI(Tl).

The absorption and emission spectra of Np4+ in ThSiO4 and ThO2 have been recorded at 4.2 K in the energy range 4000–25 000 cm−1. For ThSiO4:Np4+, 29 levels are assigned in the D2d crystal field symmetry and fitted with a least-squares routine leading to a r.m.s. of 45 cm−1. The values of the spectroscopic parameters are: F2 = 45212, F4= 38018, F6 = 28345, ζ = 2129, B02 = 333, B04 = 1515, B44= −3563, B06= −1853 and B46= −802 cm−1. For ThO2, a preliminary interpretation is given on the basis of the ThSiO4 results.

Resume Pour identifier le ou les complexes de uranium(VI) formes dans l'acide phosphorique concentre on a etudie par radiometrie α ou γ le partage de 233U ou 230U dans le systeme: HDEHP-C6H6-H3PO4, HClO4, LiOH, μ = 0,2. Le pH a varie de 0,7 a environ 4 et la concentration totale de H3PO4 est restee inferieure a 4,2 M (lg[H3PO4] ⩽ 0,4). Ces variations recouvrent celles du pH et de lg[H3PO4] que l'on trouve dans l'acide phosphorique pur de concentration inferieure a 4,2 M. Dans les phases aqueuses soumises au partage, on a identifie de nombreux complexes et mesure leur constante de stabilite a partir de UO22+ et de H3PO4. Dans H3PO4 environ 4 M qui correspond a la molarite de la solution resultant du traitement des phosphates pour obtenir l'acide phosphorique, uranium(VI) existe essentiellement sous la forme d'un complexe d'ordre 3 et de charge 1+ (85%). Ce complexe peut etre formule au moins de trois facons differentes: UO2(H2PO4)·2H3PO4+ ou UO2(H2PO4)·H6P2O8+ ou UO2(H5P2O8)·H3PO4+.

L'indexation de raies à zéro phonon du spectre d'absorption de ThBr4 : U4+ est discutée, compte tenu du spectre de vibration de la matrice et des spectres d'émission de ces monocristaux excites par laser.

Resume Les constantes de formation des complexes M HCitCit 2− et M Cit 2 3− ont ete mesurees simultanement pour Am, Cm, Cf, Es et Fm en utilisant l'extraction par solvant des elements a l'etat de chelates. Les variations des valeurs de ces constantes en fonction de Z font apparaitre la troisieme branche de la tetrade de la serie 5 f .

Absorption and emission spectra of Pa4+ in ThCl4 were recorded at different temperatures varying from 4.2 to 300 K. The seven‐crystal field states were measured experimentally and fitted to the spin‐orbit and crystal field parameters resulting from D2d symmetry. The obtained parameter values (in cm−1) are F0 = 3658, ξ = 1525, B20 = −1373, B40 = 1725, B44 = −2487, B60 = −2290, and B64 = −53. Emission occuring at 4915 and 4078 cm−1 was used to determine the 2F5/2 low lying levels.

Resume Le partage direct et en retour du plutonium trivalent entre des phases aqueuses reductrices non complexantes et des solutions benzeniques de theonyltrifluoroacetone (TTA) a eteetudie en fonction de la concentration en element, en chelatant et du pH. L'ion aquo Pu 3+ est acide; son hydrolyse monomere debute vers pH 4, et il est tres bien extrait par le TTA, caracteristiques qui le differencient nettement des autres ions M aq (AM a Es).

Resume Le partage a 150°C de l'actinium, du thorium et des elements “5f” jusqu'au californium entre l'eutectique LiNO3KNO3 et des solutions de TBP ou de TPPO dans un eutectique de polyphenyles, a ete mesure en systeme ferme, en fonction de la concentration libre en agent solvatant dans la phase organique. Les elements etaient tous a l'echelle des indicateurs. Tous les nitrates des elements extraits (sauf le protactinium) sont solvates par deux molecules d'agent extractant, excepte le thorium. Dans les conditions experimentales explorees, le comportement de cet element differe des autres, en particulier de celui du berkelium tetravalent. Cela est du a sa faible affinite pour les ions oxyde de la phase saline.

Resume La constante de formation β2 des complexes M H Cit Cit2− (M  La a Lu) a ete mesuree en utilisant l'extraction par solvant des lanthanides a l'etat de chelates, chaque element etant convenablement marque par l'un de ses isotopes radioactifs. Les experiences ont ete conduites en etudiant la distribution de plusieurs d'entre eux, afin de controler etroitement les conditions experimentales. La variation de log β2 en fonction de Z montre l'existence de l'effet tetrade qui est discute comme resultant de l'effet nephelauxetique dans la serie 4f.

Les spectres d’absorption dans l’ultraviolet de PaV en solution perchlorique, sulfurique ou chlorhydrique et de PaIV dans les deux derniers milieux ont ete mesures. On les a releves dans chaque milieu pour differentes acidites et diverses concentrations en anions et en protactinium. L’evolution des maxima d’absorption en fonction du temps a ete suivie.Un essai d’interpretation des observations les plus importantes est donne. Le maximum d’absorption vers les courtes longueurs d’onde, entre 208 et 217 mμ, que l’on retrouve dans toutes les solutions de Pa pentavalent, serait notamment associe a une transition electronique du groupement Pa = O.