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Invité 02

The needs of basic studies for nuclear waste management issues

R. Guillaumont

Académie des Sciences, Commission Nationale d'Evaluation, 39-43 quai André Citroën, 75015 Paris [email protected]

Abstract - There are several strategies to manage the radioactive matter which has taken the status of "ultimate radwaste". They are based on combinations of the three primary strategies : "Wait for Decay", "Concentrate and Confine" and "Disperse and Dilute" the radiotoxic radionuclides and chemiotoxic elements. They are, or will be used for safe storage (interim and long term) or safe disposal of nuclear wastes. The chemical needs to apply these strategies are on materials for isolation, matrices for confinement and on the numerous aspects of the migration of the elements, both in the lithosphere and in the biosphere. According to the ultimate fate of long lived radionuclides which will be finally released into the environment, migration studies of elements are, or should be, the driving force of research in nuclear wastes management. The chemical needs for improving our present basic knowledge related to this field will be reviewed, with emphasis on some new topics and on the effects of concentration of the elements when they migrate. The necessity to open some "dark boxes" will be outlined. The paper does not intend to give programs of researches but only tracks for future research.

INTRODUCTION scientific and technological point of view it covers all the steps from the initial decision to get ride the The aim of radwaste management is to protect man unusable radioactive matter to its evacuation from and the environment against radiological and the biosphere. chemical effects according to safety rules, and, with this respect, safety cases studies provide the risks Effluents are released into the environment under that must be taken into account for a safe controlled conditions, atmosphere for the gaseous management [1]. The three basic strategies to be effluents, hydrosphere for the liquid effluents. applied to reach these objectives and to minimise Radwaste packages are disposed of into risks, as long as radiological protection is surface/subsurface engineered structures or in deep considered, are : "Wait for Decay", "Disperse and geological repositories (lithosphere) or, in most of Dilute" and "Concentrate and Confine" the the cases up to now, stored in facilities waiting for a radionuclides [2]. Managing radwaste is playing future disposal. with these three strategies according the given Applying one or a combination of the three basic rules. To play there is a need of a deep knowledge strategies needs to know the behaviour of in basic and applied sciences covering many fields. radioactive solids during ageing and during a Radwaste management starts at the different steps contact with water and the behaviour of the of nuclear activities as earlier as a certain amount of radionuclides in the environment. This is obvious radioactive matter, which comes undone because it considering the ultimate fate of effluents and waste is not foreseen any use for it, is produced [1]. This packages. So it is also obvious that chemistry plays unusable matter takes the status of radwaste but an important role in waste management, both at the becomes a "real ultimate radwaste" only when an step of preparing effluents in due form to be administrative decision is taken, according to some released or conditioning the unusable radioactive policy. The radioactivity that it contains vary in matter and at the latter step, when radionuclides are tremendous limits : in a range of about 10 manifold, released in the environment. Indeed chemistry is starting from some Bq/g, as well as the type of always present when the composition of matter radionuclides : bêta, alpha and gamma emitters. changes. These two characteristics, linked with the half life Dilution of effluents or confinement of and decay modes of radionuclides, dictate its radionuclides by conditioning are not, or should not immediate or delayed fate. be independent. They are, or should be, driven by The unusable radioactive matter is usually the future behaviour of released radionuclides at the processed. Gaseous or liquid effluents and ultimate present time or at a very far future. So the driving waste in the form of solid are then obtained. force of the researches in chemistry for waste Excepted for waste coming from mining all the management is the "migration" of the radioactive resulting solids from processing are put into elements from the given place where they stand to containers. Waste packages are the end products of "man" at the given place where he will be. conditioning. According to policy, and strictly Migration must be understood as "migration in speaking, waste management is the management of lithosphere" (reducing situation) and "migration in packages, but by extension and according to a the the biosphere" (oxidising situation). This topic is so Invité 02 important that since 1987 each two years Migration packaging. Activated elements can be considered as Conferences deal with it [3]. natural elements. Many non radioactive natural elements play an important role in waste This paper gives consideration according to a management as , iron, sulphur as well as chemical point of view on the three topics which elements produced in situ, like hydrogen due to the are the pillars of a scientific waste management : corrosion of metallic materials. In principle they do chemistry for "concentrate-confine", chemistry for not belong to the list of elements of interest, even if "disperse-dilute" and chemistry for "wait of decay". the chemical behaviour of some of them in the It will focus on the radwastes from the nuclear context of radwaste management need clarification. cycle, mainly on the long lived ones, belonging to what is called the "nuclear wastes" [4]. Indeed There are at least five fields of experimental basic management of these wastes provides the chemistry which are involved in nuclear waste opportunity to check the applicability of the three management : solid state chemistry, ageing of strategies. It needs conditioning, storage and solids, aqueous chemistry, interface solid-solution geological disposal which is expected to end by a chemistry and all under ionising progressive very slow release of radionuclides and . Obviously and dilution into the aquifers of the lithosphere and then modelling must support all the experimental in a given biosphere. The case of effluent release research. Some specific well known related topics can be seen as enclosed in the previous one. are summarised in Table 1. It is easy to find where they apply in nuclear waste management. In each of Only basic research in chemistry is considered these topic too many researches have been done, because it supports strongly models used to predict and are actually going on, which prevent to do here short or long term behaviour of elements, what is complete reviews of the results obtained. There are needed. numerous international programmes. 1 - ELEMENTS TO BE CONSIDERED, In the following two points common to all the fields FIELDS AND TOPICS OF BASIC and topics mentioned will be pointed out : the role CHEMISTRY TO BE STUDIED of the concentration of the elements on their The elements to be considered in nuclear waste chemical behaviour and the role of the management are restricted in principle to those simultaneous presence of elements with near which are radiotoxic and/or chemiotoxic. The chemical properties on the formation of number of such "elements of interest" is important. compounds. Then, considerations on the main They belong to natural radioelements (, issues of waste management will be addressed, , ) found in , artificial from which needs to improve our basic knowledge radioelements ( including the different will appear. It is not intended to derive programmes kinds of man-made uranium, technetium) and of researches but only to point out some tracks. As artificial elements (fission products) both found a consequence cited references are mainly restricted initially in spent nuclear fuels (and in recycling to recent works or to general papers to give materials like fresh ) and finally examples. elements added for processing unusable radioactive matter as chemical reagents or material for

Table 1. Topics to be considered in basic chemistry for nuclear wastes issues

Conditioning of radionuclides Migration of radionuclides

Radiation chemistry and radiolysis Building up of elements in radioactive matter Composition of matrices for immobilisation Leaching of solids Speciation (inorganic, organic, living material all including colloids) in reducing and oxidising conditions Speciation at high temperature Materials for packages Diffusion and mobility of species Sorption on mineral and all including colloids Ageing under the effect of radioactivity Role of microbial organisms Re-concentration in living material

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(Fe(III)/Fe(II)) and ox /red (Np(V)/Np(IV)). In 2 - RANGE OF CONCENTRATION OF THE 2 2 man-made chemistry R is usually greater than unity ELEMENTS and M2 remain in its lower oxidation state (CFe = -8 -3 Chemical problem in nuclear waste management 10 M, CNp = 10 M). At tracer scale R is less than -8 address both classical chemistry with weighable unity and M2 could be oxidised (CFe = 10 M, CNp amount of element and tracer scale chemistry with = 10-9 M). Values of R are very sensitive to selected minute amount. Indeed in conditioning the wastes values used to make speciation and modelling. For have to transform high level radioactive instance the speciation of uranium in the following matter at kilogram scale (vitrification for instance) conditions : pH in the range 4 to 8, Eh in the range - -8 but when they deal with aquatic chemistry 120 to 120 mV (anoxic condition), CU around 10 they must experiment at 10-8 to 10-10 M to be M depend dramatically on the value used for the representative of the concentrations expected in the molar standard Gibbs energy of formation of far field of a geological repository. Variation of U(OH)4(aq). Recently this value has been changed. concentration of the elements in the near field, Accordingly at pH 8.5 with a total concentration of -4 limited by of compounds, are expected to carbon of 1.5 10 M, CU increase much more when be moderate to low. Drastic changes of elements Eh increase from - 400 mV to - 200 mV than concentration arise when effluents are released in previously expected. The change of this Gibbs water or will arise in a far future when plumes from energy of formation is based on the fact that geological repositories will reach surrounding UO2(cr) is not the water solubility limiting solid, as aquifers. During migration (advection, diffusion, believed. Solubility is limited by UO2(am, hyd). dispersion, retardation) in the lithosphere and Many and many experiments on U, but also on biosphere the concentrations of elements do not other tetravalent actinides were accumulated before decrease continuously but fluctuate at a nano scale to reach this conclusion [7]. That shows that basic between micro and nano- concentrations as ionic research chemistry has to be conducted strength does. Each solid solution interface are thin continuously with crossing methods and exploring layers sided by high gradients concentration. large conditions of parameters variations. Basic research makes the difference. All the chemical reactions experienced by elements during migration are of acido-basic or redox type. When M interacts with a solid phase the situation is They occur in anoxic or oxic conditions and in also depending on CM with respect to the critical water or in non saturated systems They concern concentration for which all active sites of the solid reactions in solution and at solid-solution interface are saturated by M, or by other element M' of close [5,6]. properties to M. The distribution coefficient of M between the two phases is a complicated function of The effect of concentrations of elements on CM, CM', CL, R and equilibrium constants, which speciation in well known, provided the equilibrium shows that the behaviour of M can be sometimes constants of reactions are known and the solutions not clearly foreseen. behave as true solutions. So in principle their behaviour can be foreseen. This can be illustrated In these considerations the kinetics of the reactions by two simple examples, even if each real situation are not taken into account because as long as one has to be analysed carefully. For instance let be reactant has a high concentration there is not a great respectively CM and CL the total concentrations of perturbation on the kinetic known in usual an element of interest, M, and a complexing agent conditions [6]. But it is obvious that when both the HL and [L] the free ligand concentration. The ratio concentrations of reactants decrease the speed of R of the concentrations of the species MLl+1 over reaction decrease and at the ultimate step MLl is a function of CL, CM, K and l, K being the disproportionation reactions for instance are not stepwise constant for the formation of MLl+1. When allowed [8]. The lacks in kinetics of acid-base and M is at tracer scale R is greater than unity, M is in redox reactions in usual conditions can first be the form MLl+1 and it is the reverse when R is less filled before to understand the kinetics in other than unity, M is mainly found in the MLl specie. An conditions. important case occurs when the charges of two When concentration of element is very low, species are of opposed sign because generally solubility product of compound ML which at high drastic changes in behaviour occur. This arise with n concentration control its solubility, is not fulfilled multi-charged anions L (for instance U(OH) aq and 4 anf ML are not likely to be formed. It is more U(OH) (CO ) 2-). In a redox reaction between M n 2 3 2 1 probable that M will be engaged in co-precipitation (ox , the element found in natural environment, 1 reactions by syncristallisation, internal sorption or Fe(III)) and M (red , the element of interest, 2 2 other processes [32]. At low concentration some Np(IV)) the ratio R of the concentration of C M2 phenomena, not yet well understood, can disturb over C is also a function of the initial M1 thermodynamic based phenomena like pseudo- concentration of M and M and of the redox 1 2 colloid formation, irreversible sorption and even potentials of the two couples ox /red 1 1 spontaneous depositions on semi-metallic solids. Invité 02

The case of unexpected migration of contact with the radioactive material inside the over long distance in a rather short time is well packages (, glasses, other chemicals). For known [29]. All of these phenomena fall in the dark metallic material the research is on corrosion box of "inorganic behaviour of trace elements " extended on the long term [9]. For no metallic it is which only starts to be open since some years (dark on chemical ageing. These topic are most often well box is not black box). Indeed colloids and co- covered by non nuclear research and specific precipitation studies know a renew of interest (see programmes on are going on. section 4). Decay allowed by the retardation of radionuclides in the lithosphere does not belong to that strategy, Another dark box is the box of "biogeochemical even if the final result are the same, the behaviour of trace elements " which is far to be disappearance of the radionuclides. understood, even if some global transfer coefficients of some elements from solutions to Chemistry for Concentrate and Confine plant and to animal are known and even if their Strategy repartition between organs, on which "behaviour There are two aspects related to this topic : model" are based for safety purpose, is also known conditioning and degradation of packages. (see section 4). Confining radionuclides is not isolating 3 - SIMULTANEOUS PRESENCE OF radionuclides. The word means that a controlled or "ELEMENTS LIKE" foreseen leak is expected at any time. It is often misunderstood. The collective behaviour of "elements like", as actinides in a given oxidation state, at more or less All chemical processes used for the conditioning of equal concentration, has not been the subject of nuclear wastes address very large quantities of high many researches. Some properties of actinides vary radioactive matter. That means that industrial smoothly like Gibbs energy of formation of oxides processes must be used and that chemical which allows to forecast a near common behaviour engineering plays an important role at the step of [23]. In solution it is expected and verified that they implementing the basic researches, which must behave independently but it is not sure that "mixed have done before. From a chemical point of view elements compounds" like , hydroxide or these researches deal with the choice of materials to more complex solid will not be formed, for instance confine the elements of interest during a "sufficient in the near field of a geological repository. Such time" with regard of the radiotoxicity of mixed solids, solid solutions or not, stoichiometric radionuclides expected to be released. The choice or non-stoichiometric, do not have properties which is, or must be, based on, ageing/corrosion/leaching are the simple addition of those of the components. investigations and on the species expected to be Moreover formation of amorphous phases which released. are not well defined, and have consequently Nuclear glasses are used and foreseen to be still formation constants rather variable in some range used as matrices for fission products and actinides of values, can also be formed, if these ranges and many other elements. It is known how to adapt overlap. Collective behaviour of elements has to be the compositions of a glass to fit with the elements studied. to be incorporated and to the industrial imperatives. 4 - CONSIDERATIONS ON CHEMISTRY/ Today a tremendous amount of results on the IN NUCLEAR WASTE microstructure, ageing and leaching of various MANAGEMENT glasses exist from which models to predict their long term behaviour are derived [10, 11]. All As already say, in the following, chemical predict a "long live" for packages of glasses placed considerations on the main issues linked to nuclear in a geological repository. Nevertheless some waste management are addressed, which bear mechanisms are not well understood as local indirectly some tracks for researches. The needs are heterogeneity and residual speed of leaching and not expressed as programmes. researches must continue. The effects of radiolysis Chemistry for Wait and Decay Strategy in under study. Research on the incorporation of larger and new amounts of radioactive compounds This strategy can be apply both in interim and long are planed and should increase. term storage and in disposal. Strictly speaking it needs man-made isolation of radionuclides, but Natural like compounds or artificial ones are sometimes it is applied allowing the release of studied as matrices for separated elements. They are small amounts of short lived radionuclides. The sintered as ceramic [12, 13]. Results on leaching basic chemistry related to these options is on the show better confinement performances than for short and long term behaviour of the first "safety glasses, but the data are not so numerous as for barrier" (fuel cladding, various containers and glasses to fully compare them. Consequently canisters) in contact with moistly air (non saturated researches must be pursued to reach the same level condition) or water (saturated condition) and in of knowledge as that for glasses. Amorphisation of Invité 02 ceramics under cumulative irradiation effects and Many have been selected in consistent databases the growth of born elements are of first importance which are the live memory of all these researches, as well as the modification of their property. when they are periodically checked [21 to 25]. But Ceramic mixtures of oxide compounds for there are still lacks on ternary compounds confining high level radioactive solutions have been (, silicates, ), on species in also studied, but not still used at industrial scale. basic solutions, on data at high temperature Section 2 has addressed the main problems linked with this Others conditionings (concrete, bitumen, ) strategy (speciation in solution and on surfaces, for radioactive matter coming from reprocessing identification of mixed solid phases of elements, have been less studied. Nevertheless basic transport parameters) and noted the existence of understanding of the leaching of elements have led "dark boxes". Migration of radionuclides as gaseous to models for the release of radionuclides which species has not been paid much attention. predict rather good confining performances. Open the "Inorganic behaviour of trace elements" Irradiated uranium and plutonium oxides in spent dark box fuels have not the same status as glasses because they cannot be considered as manufactured First at all the behaviour of nano particles of matrices. One has to accept them as they stand with inorganic compounds is not well understood in largely modified characteristics compared to non relation with solubility it is to say when surface irradiated oxides. Numerous results since 25 years phenomena become important [32]. of researches are also available on leaching in Colloids are ubiquitous in soils and waters. Thanks anoxic condition, which allow to model with a good to new powerful techniques to investigate the size confidence the release of radionuclides. But here and the formation colloids quantitative information the situation is complicated by the facts that are now available [26 to 28]. It is known from early leaching of oxides is sensitive to redox condition, to works that elements subject to hydrolysis like the presence of hydrogen and products of tetravalent actinide are good candidates for true radiolysis. Moreover tetravalent uranium has colloids formation. Today it is shown that catalytic properties which can change the behaviour equilibrium exist between true colloids and of some actinides [14, 15, 16]. hydrolysed species in solution. Pseudo inorganic For all the matrices used the research on behaviour and organic colloids or mixed colloids are also well of gas in the bulk, the "solubility" and compatibility identified. Studies on colloids can be now carried of elements as function of temperature and the out in situ [29]. microstructure must be pursued. Secondary phases Researches on structural and thermodynamic are not still well characterised [17] aspects of co-precipitation have been renewed [31 Degradation of packages and interaction of to 33]. Some systems have been investigated but materials with engineered barriers will trigger a the limited efforts done up to now should be very complex chemistry in the ill defined near field increased. of a deep repository, which is difficult to forecast as An interesting question still open is the transport a whole. Near field chemistry systems will be of properties of the species under different energy metric extension where many elements will gradients which has only poorly addressed, interact. Experiments done deal mainly with measuring only some diffusion coefficients of separated aspects of these systems, like reciprocal heavy elements in aqueous solutions. Diffusion of interaction of clay and materials of packaging, multi-charged cations and anions is not so well leaching in the presence or not of natural elements, documented as monocharged simple are. secondary phases precipitation (solid solution or Measurement of transport properties should not), co-precipitation phenomena leading to well extended to porous natural media and to gels given defined compounds or to mineral like compounds by the alteration of the surface by water. They are less defined and poorly described (structure, solids with evolutive open nanometric sized pores ), etc. The main problem is to where diffusion is restricted. Diffusion must be also predict which species will escape the near field, extended to colloids, which can migrate faster than species or true or pseudo-colloids. They will water. The field of isotopic diffusion of heavy depend mainly on the chemistry under at elements has been deserted since long time[34] the many interfaces of solids and solutions. Sorption of elements at tracer level on minerals is Chemistry for Disperse and Dilute Strategy now understood at a microscopic level [35]. The The needs clearly are on the improvement of our majority of data concern the global behaviour of comprehension of the migration processes [18 to elements with some given solids (freshly prepared 20] . Migration study is complicated because many or damaged) and simple inorganic minerals. The phenomena coupled by several retroactions are challenge is to link all the data [36]. The special involved, but we have plenty and plenty of data. case of element not limited by solubility and not Invité 02 sorbed needs attention with isotopic dilution Finally in all studies it does not be forgotten that phenomena. radwaste are radioactive and that has sometime tremendous consequences. Open the "biogeochemical behaviour of trace elements " dark box The dream in basic researches for radwaste management is to reach the modelling of the This topic starts with the speciation of elements in evolution of anthropogenic elements at multi-scale the presence of simple and then complicated into multi-phases systems. This can only be done "mimetic" organic . The next step is the with the help of simulation, a tool to be developed interaction with soil bacteria. After it must to take into account chemistry. understood how elements are picked up by plant through the organic molecules that they send in REFERENCES soils [37]. The final step of transfer from plant to animal and to man is at the border of 1. Joint convention on the safety of spent fuel radiochemistry and biology [38]. It needs speciation management and on the safety of radioactive in biologic fluids, a new growing topic [40]. waste management, International Atomic Energy Agency, INFCIRC/546, 24 December Laboratory to field extrapolation results is always 1997. This Convention was adopted on 5 difficult mainly for reducing conditions because it September 1997 by a Diplomatic Conference is difficult to have representative anoxic conditions convened by the AIEA. It has been signed by at laboratory. Consequently fields modelling of 34 countries. It gives in Article 2 the natural systems is important and for that, predictive following definitions (h and l). Definition h - codes are needed. means material in gaseous, It is clear that efforts should continue to clarify all liquid or solid form for which no further use is the phenomena involved in migration. foreseen by the Contacting party (the country that has approved the convention) or by a Chemical needs in general natural or legal person whose decision is It is obvious that basic chemistry of actinide, accepted by the Contracting party, and which especially those with changing oxidation state [39] is controlled as radioactive waste by a and fission products can only be developed with the regulatory body under the legislative and strong support of speciation and solid state regulatory framework of the Contracting investigation techniques [40]. All become more and party. Definition 1 - radioactive waste more heavy but of high performance. Coordination management means all activities, including chemistry of the elements is important, it improves decommissioning activities that relate to the speciation. A general objective is to reduce handling, pre-treatment, conditioning, storage, uncertainties on data in the contexts of their or disposal of radioactive waste, excluding variability. This is mandatory for long term off-site transportation. It may involve prediction. discharges. CONCLUSION 2. R. GUILLAUMONT, Gestion et perspective de gestion des déchets radioactifs, Technique de Chemistry in nuclear waste management must be l'Ingénieur, BN 3 660 (2002) and BN 3 661 though as a whole, because optimal conditioning to (2003) concentrate and to confine radionuclides has to be done taking into account the foreseen fate of 3. Chemistry and migration behavior of actinides radionuclides, which will be dispersed and diluted and fission products in the geosphere, into the biosphere in a known or an undetermined Radiochimica Acta, 44/45 (1988), 52/53 period of time. It is the same for the dilution (1991), 58/59, 1992, 66/67, 1994, 74, 1996, dispersion of the effluents because their chemical 82, 1998 and 88, 2000, Journal of contaminant state, when released, determine their short and long hydrology 13 (n°1/4), 1993, 21 (n°1/4), 1996, term behaviour. 26 (n°1/4), 1997, 35 (n°1/3), 1998 and 47 (n°2/4), 2001. All migration conferences cover The behaviour of the elements which constitute the the scope 1) aquatic chemistry of actinides and waste packages must be studied over large ranges fission products (solubility, dissolution, solid of the parameters governing their behaviour and in solution and secondary phase formation, many conditions, one at a time, but also all complexation with inorganic and organic together, to understand their common behaviour. ligands, redox reactions and radiolysis effects, The co-precipitation mechanisms when one element solid water interface reactions, colloids is at low concentration with regard to the formation, innovative experimental methods), concentration of the other elements is an important 2) Migration behavior of radionuclides phenomena, probably sub-estimated up to now. (sorption/desorption , diffusion and migration processes, colloids migration, effects of biological and organic materials, field and Invité 02

large scale experiments, naturals analogues), ANDRA, EDP Sciences, France 2001, pp. 27- 3) Geochemical and transport modelling (data 58. selection and evaluation, development and 15. N. P. LAVEROV, V. I. VELICHKIN, B. I. application of models, models validation) OMEL'YANENKO, S. V. YUNDINTSEV 4. Du combustible nucléaire aux déchets, od actinides during the long recherches actuelles, Guest editor E. BRÉZIN, term storage and disposal of spent nuclear C. R. Physique, tome 3, n° 7/8 (2002) fuel, Geology of deposit, 45, n°1, 1-18 5. R. GUILLAUMONT, Radiochemical (2003) approaches to the migration of elements from 16. W. BREWITZ, U. NOSECK Long term a radwaste repository, Radiochimica Acta performance of spent fuel in geological 66/67, 231-242 (1994) repositories, C. R. Physique, 3, 7/8, 879-889, 6. J. P. ADLOFF, R. GUILLAUMONT, (2002) Fundamental of Radiochemistry, CRC Press, 17. P. ZIMMMER, E. BOHNER, D. BOSBACH, Bocca Raton, 1993 J. I. KIM, E. ALTHAUS, Formation of 7. R. GUILLAUMONT, Th. FANGHÄNEL, J. secondary phases after long term corrosion of FUGER, I. GRENTHE, V. NECK, D. A. simulated HLW in brine solutions at 190 °C, PALMER, M. H. RAND, Update on the Radiochimica Acta, 90, 529-535 (2002) of uranium, 18. G. R. CHOPPIN, Actinide speciation in the neptunium, plutonium, and environment, Radiochimica Acta, 91, 645-649 technetium, Edited by F. MONPEAN, M. (2003) ILLEMASSENE, C. DOMENECH-ORTI, K. 19. P. THOULOHAT, Confinement and BEN SAID, Elsevier, 2003, pp 182-187 migration of radionuclides in a nuclear waste 8. R. GUILLAUMONT, J. P. ADLOFF, deep repository, C. R. Physique 3, 975-986 Behaviour of environemental plutonium at (2002) very low concentration, Radiochimica Acta, 20. G. DE MARSILLY, J. GONÇALVÈS, S. 58/59, 53-58 (1992) VIOLETTE, M. CASTRO, Migration 9. J. M. GRAS, Life prediction for HLW mechanism of radionuclides from a clay containers, issues related to long term repository toward adjacent aquifers and the extrapolation of corrosion resitance, C. R. surface, C. R. Physique, 945-959 (2002) Physique 3, 891-902 (2002) 21. P.VITORGE. H.CAPDEVILA, 10. I. MUNIER, J.-L. CROVISIER, B. Thermodynamic data for modelling Actinide GRAMBOW, B. FRITZ, A. CLEMENT, speciation in environmental waters, Modelling the alteration gel composition of Radiochim. Acta 91, 623-631 (2003). simplified borosilicate glasses by precipitation 22. F. MONPEAN; H. WANNER, The OECD of an ideal solid solution in equilibrium with Nuclear energy agency thermodynamical the leachant, Journal of Nuclear Materials, database project, Radiochimica Acta, 91, 617- Volume 324, Issues 2-3, 97-115 (2004) 621 (2003) 11. E. VERNAZ, Estimating the lifetime of R7T7 23. Reference 7, pp. 318-322 glass in various media, C. R. Physique, 3, 7/8, 813-825 (2002) 24. L. BION, Bassist an applied thermodynamic database for radionuclide chemistry, 12. C. GUY, F. AUBERT, J.E. LARTIGUE, C. Radiochim. Acta 91, 633-637 (2003) LATRILLE, T. ADVOCAT, C. FILLET, New conditionings for separated long lived 25. W. HUMMEL, U. BERNER, E. CURTI, F. J. radionuclides, C. R. Physique, 3, 7/8, 827-837 PEARSON, Nagra/PSI chemical (2002) thermodynamic database 01/01, Radiochimica Acta, 90, 805-813 (2002) 13. N. DACHEUX, R. PODOR, B. CHASSIGNEUX, V. BRANDEL, 26. J. ROTHE, M. A. DENECKE, V. NECK, R. M. GENET, Actinides immobilization in new MÜLLER, J. I. KIM, XAFS investigation of matrices based on solid solutions : the structure of aqueous Th(IV) species, IV IV 238 239 Th4-xM x(PO4)4P2O7, (M = U, Pu) ”, J. solloids, and solid Th(IV) Oxide/Hydroxide, Alloys and Compounds, 271/273, 236-239 Inorg. Chem. 41, 249 (2002) (1998). 27. V. NECK, R. MÜLLER, M. BOUBY, M. 14. K. SPAHIU, The chemistry of radionuclides ALTMAIER, J. ROTHE, M. A. DENECKE, in repository conditions, In "Etude pour la J. I. KIM, Solubility of amorphous Th(IV) faisabilité des stockages de déchets hydroxide - application of LIBD to determine radioactifs", Actes des Journées Scientifiques Invité 02

the solubility product and EXAFS for aqueous MO2+x(s) (M = U, Np, Pu and Am), Pourbaix speciation. Radiochimica. Acta 90, 485 (2002) diagrams. .. Nuclear Science and Technology, 28. C. BITEA, R. MÜLLER, V. NECK, C. Supplement 3, 713-716 (2002) WALTHER, J. I. KIM, Study of the 40. C. MOULIN, On the use of time-resolved generation and stability of Th(IV) colloids by laser-induced fluorescence (TRLIF) and LIBD combined with ultrafiltration. Colloids electrospray (ES-MS) for and Surfaces A 217, 63 (2003) speciation studies, Radiochimica. Acta 91, 29. D L. CLARK, The chemical complexities of 651-657 (2003) plutonium, Los Alamos Science, n° 26, p 490, (2000) 30. P. DIAZ AROCAS, J GARCIA-SERRANO, J. QUIÑONES, H. GECKEIS, B. GRAMBOW, Coprecipitation of mono-, di-, tri-, tetra- and hexavalent ions with Na- polyuranates, Radiochimica Acta 74, 51-58 (1996) 31. J. QUIÑONES, B. GRAMBOW, A. LOIDA, H. GECKEIS, Coprecipitation Phenomena of trivalent ions related to spent fuel dissolution. Part 1 : Initial experimental results and procedure, Journal of Nuclear Materials 238, 38-43 (1996) 32. G. ROUSSEAU, Coprécipitation de Th, Eu, La et Ac avec UO2 comme phase d'accueil, Thèse de doctorat de l'Université de Nantes (2002) 33. G. ROUSSEAU, M. FATTAHI, B. GRAMBOW, F. BOUCHER AND G. OUVRARD, Coprecipitation of thorium with UO2 Radiochimica Acta, 90, 523-528 (2002) 34. H. SCHONERT, Pnenomenological description of the transport of isotopes in electrolytes systems, Electrochimica Acta, 27, n° 8, 1043-1048 (1982) 35. E. SIMONI, Radionuclides retention from macroscopic to microscopic, C. R. Physique, 3, 7/8, 987-997 (2002) 36. D. KULIK, Sorption modelling by Gibbs energy minisation : towards a uniform thermodynamic database for surface complexes of radionuclides, Radiochimica Acta, 90, 815-832 (2002) 37. S. DENEUX-MUSTIN, S. ROUSSEL- DEBERT, C. MUSTIN, P. HENNER, C MUNIER-LAMY, C. COLLE, J. BERTHELIN, J. GARNIER-LAPLACE, C. LEYRAL, Mobilitité et transfert racinaire des éléments en trace, influence des micro- organismes du sol, TEC et DOC, Lavoisier, 2003 38. H. METIVIER, Toxiques Nucléaires, P; Galle editor, 2nd edition, 1997, p 225, Masson 39. P. VITORGE, H. CAPDEVILA, S. MAILLARD, M.-H. FAURE, T. VERCOUTER, Thermodynamic stabilities of