EP1454326A2 - Procede permettant de controler des etats de valence - Google Patents

Procede permettant de controler des etats de valence

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Publication number
EP1454326A2
EP1454326A2 EP20020772568 EP02772568A EP1454326A2 EP 1454326 A2 EP1454326 A2 EP 1454326A2 EP 20020772568 EP20020772568 EP 20020772568 EP 02772568 A EP02772568 A EP 02772568A EP 1454326 A2 EP1454326 A2 EP 1454326A2
Authority
EP
European Patent Office
Prior art keywords
semiconductor photocatalyst
photocatalyst
reduction
sno
doped
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP20020772568
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German (de)
English (en)
Inventor
Colin Centre for Materials Science BOXALL
Robin John Taylor
Gwenaelle Le Gurun
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National Nuclear Laboratory Ltd
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British Nuclear Fuels PLC
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Publication of EP1454326A2 publication Critical patent/EP1454326A2/fr
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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
    • G21C19/42—Reprocessing of irradiated fuel
    • G21C19/44—Reprocessing of irradiated fuel of irradiated solid fuel
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
    • G21C19/42—Reprocessing of irradiated fuel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies

Definitions

  • This invention relates to valence control and more specifically to valence control in nuclear fuel reprocessing.
  • the invention is particularly concerned with the separation of uranium from plutonium and the separation of neptunium from plutonium and uranium.
  • the non-aqueous organic phase is subjected to separation of fission products by solvent extraction and in some cases then the removal of technetium, before the so-called U/Pu split.
  • Pu(IN) is reduced to Pu(III) which is in-extractable into the non-aqueous organic phase and therefore follows the aqueous stream while the U, which is in the U(NI) state, remains in the organic stream.
  • the reducing agent used in the U/Pu split is U( ⁇ N).
  • ⁇ p(NI) in the non-aqueous solvent stream is also reduced by the U(IN) to ⁇ p(IN).
  • ⁇ p(IN) is extractable into the non-aqueous organic solvent and so exits the contactor in the non-aqueous stream with the U(NI) product.
  • the unit for carrying out the partitioning of the U and Pu in practice comprises a contactor having a multiplicity of stages, for example six stages might be used in a modern centrifugal contactor.
  • the process has two disadvantages: (i) ⁇ p is not separated from U so additional downstream processes are needed to remove ⁇ p from U; and (ii) a high excess of U(rV) reductant is required to reduce Pu(IN) to Pu(III), so reducing the value of the recovered uranium, unless 235 U enrichment of the U(IN) reductant matches that of the non-aqueous feed solution.
  • Np is present in the Purex process as a mixture of three different states: Np(IY), Np(N) and ⁇ p(NI).
  • ⁇ p(IN) and ⁇ p(NI) are both extractable into the non-aqueous solvent phase whereas ⁇ p(N) is inextractable into this phase.
  • ⁇ p is normally stabilised in the (N) state.
  • Np is typically separated from uranium during the uranium purification cycle (UP).
  • Np(IN) may be converted to ⁇ p(N) and ⁇ (NI) by heating in the aqueous phase in a conditioner at high temperature.
  • the conditioned aqueous liquor is fed to an extract and scrub mixer-settler where the ⁇ p(N) is rejected to the aqueous raffinate.
  • Any ⁇ p(NI) present in the aqueous feed may be reduced to ⁇ p(V) by a reducing agent such as hydroxylamine, which is fed to the scrub section of the contactor.
  • a reducing agent such as hydroxylamine
  • U(IN) reductant can also be a significant problem in Purex reprocessing.
  • U(IN) is initially produced at 150 g U/l (about 0.65 M) and then undergoes a series of dilutions, first to 60 g U/l (about 0.25 M) and then to 7 g/1 (about 0.03 M), at which point it is stored for a short period.
  • U(IN) exhibits some instability and is at least partially oxidised to U(NI) by nitric and nitrous acids.
  • U(IN) exhibits some instability and is at least partially oxidised to U(NI) by nitric and nitrous acids.
  • One possible mechanism for this oxidation is given by the reaction between U(IN) and nitric acid to give U(N), in the form of UO + , and nitrous acid:
  • Colloidal semiconductor particles are known to act as photocatalysts for a range of useful reactions.
  • the primary step in all of these reactions is the absorption of ultra- band gap energy photons by the particles, which generates conduction band electron- valence band hole (e " , h7) pairs within the semiconductor lattice.
  • the valence band holes can oxidise oxidisable species in solution or particle surface/lattices sites, while conduction band electrons can reduce reducible species in solution or particle surface/lattice sites, as illustrated in Figure 1.
  • the present inventors have surprisingly found that it is possible to utilise the photocatalytic properties of colloidal semiconductor particles in order to control the oxidation states of actinides in the reprocessing of nuclear fuel. Accordingly, the present invention provides a process for controlling the oxidation state of a metal ion wherein the oxidation state is deliberately changed or maintained by photocatalysis. More specifically, the invention involves the use of photocatalysis to control oxidation states or valencies, of metal ions in nuclear fuel reprocessing.
  • the process involves the addition of a particulate semiconductor photocatalyst and a soluble electron donor for the semiconductor photocatalyst to a solution containing dissolved actinide metal ions, and irradiating the semiconductor photocatalyst with electromagnetic or ionising radiation.
  • the radiation should have sufficient energy to excite the semiconductor photocatalyst.
  • the semiconductor photocatalyst may be utilised in the process of the invention in a dispersed form.
  • the particulate semiconductor photocatalyst should be removed from the solution containing the actinide metal ions. This is particularly important when the described photocatalysed processes are employed as part of a nuclear reprocessing cycle, since the solid catalyst obtained after such a solid/liquid separation adds to the overall waste requirement of the reprocessing cycle. In such cases, difficulties in the removal of the photocatalyst may be experienced when it is in a dispersed form, and means of facilitating easier removal are desirable.
  • irradiation is carried out using monochromated electromagnetic radiation, the radiation having sufficient energy to excite the semiconductor photocatalyst, and having a wavelength outside the absorption wavelength region of both the actinide and the soluble electron donor, and of a precursor substance capable of producing a derivative which promotes inhibition of the desired actinide reduction reaction.
  • the solution content of the system is further modified by the addition of a soluble stabiliser for actinide metal ion reduction, the stabiliser being capable of suppressing the action of any photogenerated substance that may promote inhibition of the desired reduction reaction.
  • the electron donor for the semiconductor photocatalyst and the stabiliser for actinide metal ion reduction are one and the same component.
  • suitable particulate semiconductor photocatalysts for use in the present invention, it is necessary that certain performance criteria should be provided.
  • suitable materials are required to have the following properties:
  • SnO 2 can be identified as a candidate semiconductor for valence control applications in nuclear fuel reprocessing systems. This can be achieved by study of the potential-pH diagram for the Sn-H 2 O system overlaid with SnO 2 conduction band edge, as shown in Figure 2. Inspection of this diagram indicates that SnO is thermodynamically stable over the pH range -2 to 16 and is not prone to any photocathodic decomposition reaction. Investigation of relative positions of the tin oxide band edges with respect to areas of stability on the U-H 2 O system, Np-H 2 O system and Pu-H 2 O system potential-pH diagrams provides an indication of the suitability of SnO 2 as a photocatalyst for actinide metal ion reduction. This process then allows identification of a pH range where illuminated colloidal SnO 2 facilitate the aqueous phase separation of Np from Pu species during the Purex process. Similar conclusions are possible for TiO 2 and ZrO 2 systems.
  • EA is the electron affinity
  • E e is the energy of free electrons on the hydrogen scale
  • E cs ° is the energy of conduction band electrons at the point of zero zeta potential (pzzp).
  • the electron affinity of the material is estimated based on its electronegativity.
  • the electronegativity, X, of a semiconductor is assumed to be identical with the mid band gap energy, 72(E C + Ey). Specifically, EA is given by
  • X for the semiconductor is given by the geometric mean of the electronegativities of the composite atoms, e.g. for SnO 2 , the conduction band edge at the pzzp is given by:
  • the conduction band edge of SnO 2 may be rendered more oxidising - such that it lies in the potential range 1.24 to 1.44 N vs SHE at 1 > pH > -1 and is thus thermodynamically capable of the simultaneous generation of ⁇ pO 2 + from NpO 2 2+ , and stabilisation of PuO 2+ - by the addition to the material lattice of an appropriate dopant. Equation (3) allows calculation of the energy of the conduction band edge at the pzzp, which for SnO 2 based materials is at about pH 4.3.
  • the value of the energy of the conduction band edge decreases by 0.059 eN per pH unit, implying that the potential of the conduction band edge of doped SnO 2 should have a value of about 1.1 V vs SHE at pzzp, if that material is to photocatalytically drive the desired actinide valence control at 1 > pH > -1.
  • the potential of the conduction band edge of SnO 2 at pH 4.3 is about 0.45 vs SHE, this requires that tin oxide be doped with a metal that is
  • the doped particle may be enclosed in a sheath of undoped SnO 2 .
  • the electron donor suitable for use in the present invention is one capable of irreversibly undergoing oxidation - either by virtue of the valence holes formed by the photo-excitation of the semiconductor photocatalyst or by means of the hydroxide radicals generated by the oxidation of water by the same valence band holes - to supply electrons.
  • Suitable materials include organic acids such as formic acid, acetic acid and the like; alcohols, for example methanol and ethanol; aldehydes, including formaldehyde and acetaldehyde; amino acids; and hydrazine and its oxidation products, for examples, hydroxylamine, dihydroxylamine and the like.
  • the stabiliser for actinide metal ion reduction suitable for use in the present invention is one capable of irreversibly undergoing oxidation by a derivative that may promote inhibition of the desired reduction reaction, this derivative having been generated by the action of electromagnetic or ionising radiation on a precursor substance.
  • the precursor substance is nitric acid and the photogenerated substance that may promote inhibition of the desired reduction reaction is nitrous acid; in such cases, suitable stabilisers include hydrazine and its oxidation products, including hydroxylamine and d ydroxylamine.
  • the present invention also provides a process for reprocessing nuclear fuel to form a fissile material, optionally in the form of a fuel pellet, a fuel pin or a fuel assembly, the process involving the use of the metho of the invention. From the above considerations, it is clear that the use of unmodified SnO 2 in such applications would be particularly suitable, and this is confirmed by a consideration of its photochemistry in such systems.
  • the primary step may be considered to be the photonic generation of electrons and holes, which is denoted as proceeding with a rate g:
  • colloidal SnO 2 is irradiated in nitric acid environments typical of reprocessing liquors, the following photolysis of HNO 3 may occur concurrently with the generation of conduction band electrons and valence band holes:
  • Neptunium species in the reprocessing liquor may then react as follows:
  • the NpO 2+ species may then react with HNO 2 (generated as a result of the photolysis of HNO 3 ) as follows:
  • the photocatalytic process exploits the direct reduction of Np and Pu ions using photogenerated conduction band electrons and may be described as follows.
  • the primary step may be considered to be the photonic generation of electrons and holes, which is denoted as proceeding with a rate g:
  • neptunium species in the liquor may then react as follows:
  • titanium dioxide has also been identified as a potentially promising semiconductor for valence control applications.
  • a consideration of the photochemistry of TiO 2 in nuclear reprocessing liquor shows that the band edge positions of this material are such that the conduction band has a potential of +0.15 N vs SHE, and the valence band has a potential of +3.35 V vs SHE.
  • Thermodynamic calculations indicate that when TiO 2 is subjected to ultra-band gap illurnination, the photogenerated conduction band electrons are energetic enough to reduce TiO 2 to Ti 3+ at pH ⁇ 0, while the concomitantly produced valence band holes may oxidise TiO 2 to TiO 2 2+ at pH ⁇ 1.
  • illuminated TiO 2 may be expected to undergo photoanodic dissolution at pH ⁇ 1 and both photoanodic and photocathodic dissolution at pH ⁇ 0.
  • the energetics of its conduction band in particular, do render TiO 2 attractive for photocatalytic valence control purposes at solution pH > 1.5.
  • Ultra-band gap illumination of TiO 2 in the presence of Np, Pu and U ions at pH 1.5 will result in the conduction band electron-driven generation of Pu 3+ , U 4+ and insoluble NpO 2 , presenting a possible extraction route for Np.
  • the process of the present invention is preferably performed in the presence of a stabiliser for actinide metal ion reduction, and the role of this stabiliser will how be considered. If the semiconductor photocatalyst is irradiated in nitric acid environments typical of reprocessing liquors, the following photolysis of HNO 3 may occur concurrently with the generation of conduction band electrons and valence band holes:
  • the nitrous acid, HNO is capable of oxidising U(IN) to U(NI):
  • U(IN) and Pu(III) being stabilised against reoxidation, so rendering the uranium and plutonium separable by solvent extraction.
  • a particularly preferred embodiment of this system is achieved when the electron donor for the semiconductor photocatalyst and stabiliser for actinide metal ion reduction are one and the same material, i.e. hydrazine is employed as both the stabiliser and the electron donor for the semiconductor photocatalyst.
  • Figure 1 shows the primary reactions occurring at a particulate semiconductor photocatalyst illuminated by electromagnetic radiation of sufficient energy to photoexcite the photocatalyst
  • FIG. 7 shows the concentration of Ce(III) as a function of illumination time.
  • the Ce 3+ is generated by photocatalysed reduction of Ce 4+ , achieved through illuminating with light of wavelength 312 nm a solution containing 0.12 mol Ce 4+ m “3 , 55 mol ethanol m “ and 100 g SnO m " . Illumination is removed at 920 s;
  • Figure 8 shows the concentration of U(IN) as a function of illumination time.
  • the U 4+ is generated by photocatalysed reduction of UO 2 2+ , achieved through illuminating, with light of wavelength 312 nm, a solution containing 10 mol UO 2 2+ m "3 , 55 mol ethanol m “3 and 100 g SnO 2 m "3 ;
  • Figure 9 shows the concentration of photogenerated U(IV) as a function of time for the solution of Figure 8 after the source of illumination has been removed;
  • Figure 10 shows the concentration of U(IN) as a function of illumination time.
  • the U 4+ is generated by photocatalysed reduction of UO 2 2+ , achieved through illuminating, with light of wavelength 350 nm, a solution containing 10 mol UO 2+ m "3 , 100 g SnO 2 m “3 and either 550 mol ethanol m “3 (Series 1), or 550 mol hydrazine m "3 (Series 2);
  • Figure 11 shows the concentration of photogenerated U(IN) as a function of time for the solution of Figure 10, Series 1, after the source of illumination has been removed
  • Figure 12 shows the concentration of photogenerated U(IV) as a function of time for the solution of Figure 10, Series 2, after the source of illumination has been removed;
  • FIG. 13 shows the following two scenarios: Series 1 : Concentration of U(IN) as a function of illumination time.
  • the U 4+ is generated by photocatalysed reduction of UO 2 2+ , achieved through illuminating, with light of wavelength 350 nm, a one solvent phase, aqueous solution containing 10 mol UO 2 2+ m "3 , 100 g SnO 2 m "3 and 550 mol hydrazine m "3 ;
  • Series 2 Concentration of U(IN) in tributyl phospahate as a function of illumination time.
  • the U 4+ is generated by photocatalysed reduction of UO 2 2+ , achieved through illuminating, with light of wavelength 350 nm, a two solvent phase system - one solvent phase being an aqueous solution initially containing 10 mol UO 2 2+ m "3 , 100 g SnO 2 m " and 550 mol hydrazine m " , the other solvent phase initially containing only tributyl phosphate;
  • Figure 14 shows the concentration of photogenerated U(IN) as a function of time for the non-aqueous solvent phase of Figure 3, Series 2, after the source of illumination has been removed;
  • Figure 15 shows the concentration of U(IN) as a function of illumination time.
  • the U 4+ is generated by photocatalysed reduction of UO 2 2+ , achieved through illuminating, with light of wavelength 350 nm, an aqueous solution containing 10 mol UO 2 2+ m “3 , 0.05 mol Ce 4+ m “3 , 100 g SnO 2 m “3 and 550 mol hydrazine m “3 .
  • Irradiation of the photocatalyst is conducted at 350 nm as light of this wavelength has energy high enough to excite the semiconductor photocatalyst and is outside the absorption wavelength region of nitric acid, so avoiding the photogeneration of nitrous acid.
  • Nitrous acid is capable of reoxidising the photocatalytically generated U(IV) back to U(VI) (vide supra).
  • the invention therefore also envisages processes wherein semiconductor photocatalysed reduction of metal ions occurs in one of two solvent phases - one aqueous and one non-aqueous - in contact, and wherein, as a result of that reduction, the reduced metal ion is selectively retained by one of the solvent phases - either the phase it originated in, or as a result of a phase transfer reaction.
  • Figure 13 also shows that, upon illumination, the concentration of U(IN) in the tributyl phosphate phase, which was initially zero, increases with illumination time as a result of photocatalysed reduction of UO 2 2+ originating from the aqueous phase.
  • the concentration of U 4+ in the tributyl phosphate phase continues to increase until it is equal to the original concentration of U(VI) in the aqueous phase.
  • spectroscopic measurements indicate that the concentration of both U(IN) and U(VI) in the aqueous phase is virtually zero, indicating that 100% of the U(NI) has been reduced to U(IN) and transferred from the aqueous phase to the non-aqueous phase.
  • Figure 13 also compares this two phase data with the comparable one phase data of Figure 10 and it can be seen that the rates of U(IN) evolution are virtually identical, suggesting that the semiconductor photocatalysed reduction of U(VI) to U(IN) occurs almost exclusively in the aqueous phase, and that it is then followed by a fast phase transfer of U(IN) to the non- aqueous phase.
  • Figure 14 is shown the concentration of photogenerated U(IN) as a function of time elapsed after the removal of illumination from the non-aqueous component of the two solvent phase system generated as a result of the experiment conducted in the presence of hydrazine shown in Figure 13.
  • the invention also envisages processes wherein semiconductor photocatalysed reduction of two or more types of metal ion occurs simultaneously.
  • an experiment was conducted to assess the effect of the presence of more than one type of reducible metal ion on process efficiency.
  • a first preferred embodiment of the present invention envisages a photocatalytic process which comprises a spent fuel reprocessing method in which an aqueous liquor containing U(NI) and Pu(IV) is combined with a photocatalyst and illuminated to reduce Pu(IV) to Pu(III) and U(VI) to U(IN).
  • a suitable photocatalyst comprises any metal oxide, doped metal oxide or mixed metal oxide that is demonstrably thermodynamically or kinetically stable under some or all of the chemical and radiolytic conditions employed during nuclear reprocessing, and is preferably selected from SnO 2 , TiO 2 , ⁇ b 2 O s , Ta 2 O 5 , WO 3 , ZrO 2 , BaTiO 3 or SrTiO 3 .
  • the Pu(ffi) is inextractable into organic solvent and may therefore be separated from the U which is extractable.
  • this liquor may be subjected to solvent extraction using an organic solvent, to extract the U into the organic solvent phase and leave the Pu(III) in the aqueous phase.
  • a photocatalytic process comprising a spent fuel reprocessing method wherein an aqueous liquor containing ⁇ p(VI) is combined with a photocatalyst and illuminated to reduce Np(NI) and ⁇ p(N) to ⁇ p(IN).
  • Suitable photocatalysts comprise any metal oxide, doped metal oxide or mixed metal oxide that is demonstrably thermodynamically or kinetically stable under some or all of the chemical and radiolytic conditions employed during nuclear reprocessing, and are preferably selected from SnO 2 , TiO 2 , ⁇ b 2 O 5 , Ta 2 O 5 , WO 3 , ZrO 2 , BaTiO 3 or SrTiO 3 .
  • Np(IN) is insoluble in aqueous solution at ' pH values greater than -0.5, solution acidities of pH less than 0 being typical of those acidities encountered in nuclear reprocessing.
  • ⁇ p(IV) is insoluble in the aqueous phase and will precipitate and may therefore be separated from uranium and plutonium which are soluble.
  • the aqueous liquor typically contains U(VI) and Pu(IV), both of which are extractable into the organic solvent.
  • the Pu(IV) undergoes photocatalysed reduction to Pu(ffl), which is inextractable into organic solvent, whilst the U(NI) is reduced to U(IN), which is extractable; after the photocatalysed reduction of ⁇ p(NI) to ⁇ p(IN), and its subsequent separation by precipitation, and the photocatalysed reduction of Pu(IN) to Pu(III), this liquor may be subjected to solvent extraction, using an organic solvent, to extract the U into the non-aqueous solvent phase and leave the Pu(III) in the aqueous phase.
  • a third preferred embodiment of the present invention concerns a photocatalytic process comprising a spent fuel reprocessing method in which an aqueous liquor containing ⁇ p(NI) is combined with a photocatalyst and illuminated to reduce ⁇ p(NI) to ⁇ p(N).
  • the photocatalyst comprises any metal oxide, doped metal oxide or mixed metal oxide that is demonstrably thermodynamically or kinetically stable under some or all of the chemical and radiolytic conditions employed during nuclear reprocessing, and is preferably selected from SnO 2 , TiO 2 , ⁇ b 2 O 5 , Ta 2 O 5 , WO 3 , ZrO 2 , BaTiO 3 or SrTiO 3 .
  • the Np(N) is inextractable into organic solvent and may therefore be separated from uranium, which is extractable.
  • the liquor typically contains U(NI) and Pu(IV), which are extractable into organic solvent and, by judicious choice of a photocatalyst with the appropriate conduction band edge energetics, are unchanged by the photocatalysis procedure, as well as ⁇ p(NI); after the photocatalysed reduction of ⁇ p(VT), this liquor may be subjected to solvent extraction using an organic solvent, to extract the U(NI) and Pu(IN) into the solvent phase and leave the ⁇ p(N) in the aqueous phase.
  • a variation of the third preferred embodiment envisages a process comprising a further treatment with a second type of photocatalyst, said treatment being conducted in accordance with the first preferred embodiment, so achieving sequential removal of Np(V) to the highly active waste stream by a photocatalysed process, followed by separation of Pu(i ⁇ ) from U by a second photocatalysed process.
  • a particularly preferred photocatalyst for reducing Np(VI) and Np(V) to Np(IV), and reducing Pu(TV) to Pu(II ⁇ ) and reducing U(NI) to U(IN) is SnO 2 ; another preferred catalyst for this reduction is TiO 2 , provided that the pH of the aqueous liquor does not fall below 1.5.
  • ZrO 2 is also a preferred material, since it shows adequate chemical stable at pH 0 and is suitable for reducing species, its conduction band having a potential of about —1 V versus the standard hydrogen electrode at pH 0.
  • a fourth preferred embodiment of the invention is concerned with the use of the photocatalyst to effect the reduction of U(VI) to U(IN) ions in an aqueous liquor, particularly nitric acid solution, wherein the U(IN) ions will subsequently be used as process reagents.
  • the photocatalyst comprises any metal oxide, doped metal oxide, or mixed metal oxide that is demonstrably thermodynamically or kinetically stable under some or all of the chemical and radiolytic conditions employed during U(IN) generation, and is preferably selected from SnO 2 , TiO 2 , ⁇ b 2 O 5 , Ta 2 O 5 , WO 3 , ZrO 2 , BaTiO 3 or SrTiO 3 .
  • the preferred photocatalyst is SnO2, which has been demonstrated to be particularly suitable for this purpose.
  • This embodiment of the invention also envisages the photocatalytic stabilisation of the U(IV) ions, which may or may not have been actually generated photocatalytically during subsequent dilution and storage, before use within a nuclear reprocessing plant.

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Abstract

La présente invention concerne un procédé de contrôle de l'état d'oxydation d'un ion métallique, l'état d'oxydation ou la valence de l'ion métallique étant modifié(e) ou conservé(e) par photocatalyse. Ce procédé comporte, de préférence, le contrôle de l'état d'oxydation ou de la valence d'ions métalliques dans le retraitement du combustible nucléaire et, de préférence, l'adjonction d'un photocatalyseur semi-conducteur particulaire et d'un donneur d'électron soluble destiné au photocatalyseur semi-conducteur, dans une solution contenant des ions métalliques d'actinide dissous ainsi que l'exposition du photocatalyseur semi-conducteur à des rayons électromagnétiques ou ionisants. Ce procédé comprend également un système qui est davantage modifié par l'addition d'un stabilisant soluble pour la réduction d'ions métalliques d'actinide, le stabilisant permettant de supprimer l'action d'une substance photogénérée quelconque qui peut favoriser l'inhibition de la réaction de réduction souhaitée. Le procédé évite les processus de retraitement complexes qui sont associés aux procédés de l'état de la technique.
EP20020772568 2001-10-30 2002-10-30 Procede permettant de controler des etats de valence Withdrawn EP1454326A2 (fr)

Applications Claiming Priority (3)

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GB0125951 2001-10-30
GB0125951A GB0125951D0 (en) 2001-10-30 2001-10-30 Process for controlling valence states
PCT/GB2002/004875 WO2003038836A2 (fr) 2001-10-30 2002-10-30 Procede permettant de controler des etats de valence

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JP (1) JP2005508244A (fr)
KR (1) KR20050040853A (fr)
CN (1) CN1578989A (fr)
AU (1) AU2002337328A1 (fr)
GB (1) GB0125951D0 (fr)
RU (1) RU2004115750A (fr)
WO (1) WO2003038836A2 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009135163A2 (fr) 2008-05-02 2009-11-05 Phoenix Nuclear Labs Llc Dispositif et procédé pour produire des isotopes médicaux
WO2012003009A2 (fr) 2010-01-28 2012-01-05 Shine Medical Technologies, Inc. Chambre de réaction segmentée pour production de radio-isotope
EA028199B1 (ru) * 2010-12-21 2017-10-31 Сайтек Текнолоджи Корп. Микродисперсии гидроксаматных полимеров и способы их получения и их применения
US10734126B2 (en) 2011-04-28 2020-08-04 SHINE Medical Technologies, LLC Methods of separating medical isotopes from uranium solutions
RU2649662C2 (ru) * 2012-04-05 2018-04-05 Шайн Медикал Текнолоджиз, Инк. Водная сборка и способ управления
CN103896345A (zh) * 2014-02-27 2014-07-02 中国原子能科学研究院 Nox氧化调节钚价态的方法和装置
RU2726224C1 (ru) * 2019-12-11 2020-07-10 Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" Способ концентрирования жидких радиоактивных отходов
CN112695213B (zh) * 2020-12-03 2022-09-09 北京工业大学 一种酸浸耦合光还原提取废fcc催化剂中稀土的方法

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1592425B1 (de) * 1967-06-16 1970-12-10 Kernforschung Gmbh Ges Fuer Verfahren zur Gewinnung von Neptunium neben Uran und Plutonium aus bestrahlten Kernbrennstoffen
JPH06102148B2 (ja) * 1986-01-22 1994-12-14 株式会社日立製作所 溶存物質の酸化又は還元方法及びその装置
EP0233498B1 (fr) * 1986-01-22 1991-08-21 Hitachi, Ltd. Procédé et installation pourla réduction de métaux precieux par photoélectrocatalyse en solution acide nitrique
JP2640527B2 (ja) * 1989-02-07 1997-08-13 株式会社日立製作所 硝酸溶液中溶存物質の酸化方法及び装置
JPH08193B2 (ja) * 1993-01-18 1996-01-10 株式会社日立製作所 核燃料再処理廃液の処理方法
US5849200A (en) * 1993-10-26 1998-12-15 E. Heller & Company Photocatalyst-binder compositions
JPH08117588A (ja) * 1994-10-20 1996-05-14 Fujikura Kasei Co Ltd 電界凝集型流動性粉体とこれを用いた装置
GB9603059D0 (en) * 1996-02-14 1996-08-28 British Nuclear Fuels Plc Nuclear fuel processing

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03038836A2 *

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CN1578989A (zh) 2005-02-09
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JP2005508244A (ja) 2005-03-31
WO2003038836A3 (fr) 2003-12-31
RU2004115750A (ru) 2005-05-27
KR20050040853A (ko) 2005-05-03

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