Metal-metal bonded cluster complexes represent one of the important groups of compounds of group 7 elements, technetium and rhenium. While the chemistry of rhenium-rhenium bonded cluster complexes has developed extensively in these years, corresponding chemistry of technetium remains largely unrevealed. A general rule to classify the metal-metal bonded structural cores in terms of the number of d electrons, is presented, and existing Re-Re bonded cluster complexes are summarized accordingly. Recent progress of hexarhenium cluster complexes has been introduced as a typical example. From these overviews on the Re-Re cluster complexes, it is suggested that the chemistry of Tc-Tc bonded cluster complexes is highly promising.

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Technetium (I) carbonyl complexes such as [Tc (CO) ₃ (salbut) ]₂ (salbut=2- (1-butylnitrilomethylidyne) phenolato), Tc (CO) ₃ (salbut) (CH₃CN) and Tc (CO) ₃ (salbut) (py) (py=pridine) with Schiff base ligands were synthesized. The dinuclear complex [Tc (CO) ₃ (salbut) ]₂ is the first phenoxo-bridged dinuclear technetium complex. From X-ray crystallography, this dinuclear complex was revealed to be a “dimer” composed of two Tc (CO) ₃ (salbut) subunits bridged by two oxygen atoms of the salbut ligand. The two Tc (CO) 3 (salbut) subunits are in inversion symmetry each other. Schiff base Hsalbut loses a phenol proton through the ligand exchange reaction and coordinates to the technetium atom as a bidentate ligand with nitrogen and oxygen atoms. Three carbonyl ligands coordinate to the technetium atom in a facial configuration. Structures of [Tc (CO) ₃ (salbut) ]₂ in solvents were investigated by NMR and UV-vis spectroscopy. The mononuclear complex Tc (CO) ₃ (salbut) (solv) (solv=solvent molecule) was formed in strong Lewis base solvents like acetonitrile and pyridine. In weak Lewis base solvents like dichloromethane and benzene, on the other hand, the dinuclear [Tc (CO) ₃ (salbut) ]₂ complex was stable.

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The 1:1 reaction of ((C₂H₅) ₄N) ₂[fac-TcCl₃ (CO) ₃] with 2, 2'-bipyridine (bpy) gave fac-[TcCl (CO) ₃ (bpy) ] ([1]). The complex [1] is characterized on the basis of electronic absorption and ¹H NMR spectra along with single crystal X-ray analysis. The complex [1] crystallizes in the orthorhombic space group Pca2₁, with a=25.027 (3) Å, b=6.5327 (7) Å, c=16.679 (2) Å, V=2726.9 (6) Å, Z=8, and R=0.0320. In [1], Tc (I) ion is coordinated by three carbonyls with the facial positions, one chloride, and one bpy ligand. The metal-to-ligand charge transfer transition band was observed at 354 nm in CH₃CN solution. The transition energy of the metal-to-ligand charge transfer band for [1] is somewhat larger than that for the Re congener.

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The molecular structure and electrochemical properties of the title complex, 1, are reported. Single-crystal X-ray diffraction study reveals that complex 1 consists of two distinct metal centers, fac-{ReO₃}⁺ and fac-{Re (CO) ₃}⁺, which are bridged by tpen in a k³-k³ coordination mode with a minimal metal-metal interactions (Re…Re=7.660 (1) Å). Complex 1 undergoes irreversible reduction and oxidation in 0.1 M n-Bu₄NPF₆-CH₃CN, which are associated with the two metal centers, fac-{ReO₃} and fac-{Re (CO) ₃}⁺.

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The crystal structure of the Re0Cl₃ (PPh₃) (NCP) (PPh₃=triphenylphosphine and NCP=N-cyclohexy1-2-pyrrolidone) complex was determined by a single-crystal X-ray diffraction method. It was found that NCP coordinates to the trans-position of the oxo group, Re=O, and that the Re (V) center is in a distorted octahedral geometry. The equilibrium reaction of ReOCl₃ (PPh₃) ₂ + NCP ↔ ReOCl₃ (PPh₃) (NCP) + PPh₃ was examined, and its equilibrium constant was determined as 0.33±0.1 in CH₂Cl₂ at 25°C. Kinetic studies were carried out for the forward and backward reactions, and revealed that the rate determining steps for the both reactions are dissociation of the coordinated ligand from the Re center. Taking into account of geometrical isomers of the ReOCl₃ (PPh₃) ₂ complex, a reaction mechanism was proposed.

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The versatility of aniline derivatives as ligands for Re (V) and Tc (V) has been investigated. The reaction of (n-Bu₄N) [MOCl₄] (M=Re, Tc) with 1, 2-diaminobenzene (H₂dab) and 2, 3-diaminopyridine (H₂dap) gave the products (Bu₄N) [MO (dab) ₂] (1) and [MO (dapH) ₂]Cl (2) respectively. Both chelates in 1 and 2 are coordinated as diamides; however, in 2 the pyridine nitrogens of dapH are protonated. With trans-[ReOCl₃ (PPh₃) ₂] as a starting complex, a number of products were isolated, depending on the reaction conditions. For example, with 3-hydroxy-1, 2-diaminobenzene (H₂dab-OH) under N₂, [Re (dab-OH) Cl₃ (PPh₃) ₂] (3) was produced, in which dab-OH substituted the oxo group and is coordinated as a monodentate imide. With 3-nitro-1, 2-diaminobenzene (H₂dab-NO₂), the oxo-free complex [ReCl (PPh₃) (dab-NO₂) ₂] (4) was obtained, with bidentate diamido coordination of each chelate. Using trans-[ReO₂ (py) ₄]Cl as a starting complex, complexes of the type [Re (sbqdi-OH) ₃]Cl (5) and cis-[ReO₂ (Hdab) (py) ₂] (6) were isolated, where sbqdi-OH coordinates as the monoanionic semibenzoquinonediimine and Hdab as a bidentate monoamide. The crystal structures of these complexes are discussed in this account.

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Rhenium (V) complexes with the following multidentate dipyridyl ligands were prepared: 2, 2'-dipyridylamine (DPA), 1, 2-bis (2-pyridyl) ethylene (DPE) and di- (2-picolyl) amine (HDIPA). Reactions of a twfold molar excess of the potentially NN donor ligand DPA with trans-[ReO (OEt) Cl₂ (PPh₃) ₂] in ethanol led to isolation of a monomer [ReOCl₂ (OEt) (DPA) ] (1). Treatments of traps-[ReOCl₃ (PPh₃) ₂] with a tenfold molar excess of DPA in ethanol at reflux yielded [ReO₂ (dpa) ₂]Cl (2), but with a twofold molar excess a dimer (μ-O) [{ReOCl₂ (dpa) }₂] (3a) was isolated. The latter reaction with (n-Bu₄N) [ReOCl₄] as starting material in ethanol at room temperature led to a dark green product, also with the formulation (μ-O) [{ReOCl₂ (dpa) }₂] (3b). Reacting equimolar quantities of (n-Bu₄N) [ReOCl₄] and HDIPA in acetone led to [ReOCI (OH₂) (DIPA) ]Cl (4) in which HDIPA acted as a monoanionic terdentate chelate. The reaction of trans-[ReOCl₃ (PPh₃) ₂] with DPE, in which DPE undergoes a metal-promoted nucleophilic attack by a water molecule, produces a complex with a general formula [ReO (DPE. OH) Cl₂] (5).

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This article gives a brief summary about the current status of radiochemistry and radiopharmaceutical chemistry as related to the fac-[^99mTc (OH₂) ₃ (CO) ₃]⁺ and fac-[⁹⁹Tc (OH₂) ₃ (CO) ₃]⁺ synthon. Since the synthesis and availability of synthons or direct precursors for the labeling of biomolecules (and for the exploration of fundamental inorganic and organometallic chemistry) is a crucial prerequisite for developing new radiopharmaceuticals, some consideration about composition and characteristics of such complexes are discussed at the beginning and their suitability is discussed. Beside widely investigated basic and applied Tc chemistry in the oxidation state (V) with the [Tc=O]³⁺or [Tc=N]²⁺ moieties, the aforementioned [^{99 (m)} Tc (CO) ₃]⁺ and [⁹⁹Tc (CO) ₃]⁺ core are new members in this group. Although its pressureless synthesis from organic solvents has been described about eight years ago, it is only recently that exploitation of its radiopharmaceutical potential could reasonably start owing to the availability of a routinely applicable kit. We will summarize basic coordination chemistry of the [^{99 (m)} Tc (CO) ₃]⁺ and [⁹⁹Tc (CO) ₃]⁺ moieties as relevant for radiopharmaceutical purposes, focusing on some fundamental reactions in the context of low valent Tc chemistry. Due to its special properties, new research directions possible only through its very special physico-chemical properties will be emphasized as well.

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When ^99mTc was first applied to radiopharmaceuticals for diagnostic nuclear medicine, major efforts were focused on the development of ^99mTc complexes for excretory organs such as the liver and kidney. Over the past 30 years, a significant advance was made in technetium chemistry and radiopharmaceutical design. Now, ^99mTc radiopharmaceuticals for measuring regional cerebral and myocardial blood flow are available in clinical studies. More recently, transporter functions of the brain can also be visualized with ^99mTc radiopharmaceuticals. In this manuscript, recent advances in ^99mTc radiopharmaceuticals will be briefly reviewed.

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The aim of this work was to study products produced in basic and acidic media upon atmospheric pressure and high-pressure carbonylation and to propose probable mechanism of reaction. It was found that tricarbonyltechnetium (I) fragment forms strong complexes with charged ligands. The polydentate anions (like citrate anion), which occupies three coordination places in octahedral technetium arrangement forms strongest complexes. So Tc (CO) ₃ moiety in aqueous solutions exhibits properties of a typical d-element and a “soft” acid.

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The aim of this work was to synthesize and study complexes of M (CO) ₃⁺ with dithiocarbamate ligands included morpholine moiety which have high affinity to melanoma. The corresponding complexes of rhenium (A and B) were obtained by simultaneous mixing of bidentate (dithiocarbamate) and monodentate (isonitrile) ligands with [Re (CO) ₃Br₃][NEt₄]₂. For the comparative evaluation of these technetium-99m complexes for diagnostics of melanoma the study of affinity of these complexes to the cells of melanoma B 16 in vitro was carried out.

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Applicability of newly developed PZC (poly zirconium compound) to an adsorbent for a¹⁸⁸W/¹⁸⁸Re generator system was investigated for long term. The PZC generator gave reproducible ¹⁸⁸Re elution yields (60-75%) with 0.03% of ¹⁸⁸W parent breakthrough during 154 days corresponding to twice of the half-life of ¹⁸⁸W (69.4 d). Furthermore, the labeling yields of hydroxyethyliden diphosphonic acid and mercaptoacetyltriglycine with ¹⁸⁸Re eluted from the PZC column were high enough and there was no significant different with the results using ¹⁸⁸Re eluted from the alumina system. The ¹⁸⁸W/¹⁸⁸Re generator prepared by PZC indicated a good performance for the practical use.

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The labeling of MAG3 with carrier-free ¹⁸⁸Re from the ¹⁸⁸W/¹⁸⁸Re generator was investigated by the direct Snreduction (solid-phase synthesis) and the indirect labeling method using citrate or gluconate as a transfer ligand. Optimum pH range were 12.1-12.6 for the direct Sn reduction, 2-5 for the use of citrate and 2.6-3 for the use of gluconate. Although the differences of the optimum conditions such as pH and reaction time at room temperature were observed by using a different transfer ligand, the labeling yield of ¹⁸⁸Re-MAG3 synthesized by the all methods was over 90% under the optimum conditions. The solid-phase synthesis requires the operation under a stream of nitrogen gas and the evaporation of solvent. On the other hand, the method using a transfer ligand is one-pot preparation by just heating a reaction mixture. Thus, judging from the ease of operations, the method using a transfer ligand is more convenient.

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The technetium isotope ⁹⁹Tc is a major fission product from nuclear reactors. Because ⁹⁹Tc has few applications outside of scientific research, most of this technetium will ultimately be disposed of as nuclear waste. Geochemical modeling of the dissolution of nuclear waste, and of the solubility and speciation of the dissolved radionuclides in groundwaters, is an important part of the Performance Asssessment of the safety of a nuclear waste repository that relies on the availability of a critically-assessed thermodynamic database. Such a database for technetium was published in the book Chemical Thermodynamics of Technetium, covering the published literature through 1998. This database is described here, along with a discussion of more recent relevant studies. Gaps in the knowledge of the chemical and thermodynamic properties of technetium are identified here, and recommendations are made for measurements that are required to eliminate these gaps.

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Recent progress in production and chemistry of the transactinide elements, element 107 bohrium (Bh) and element 104 rutherfordium (Rf), is reviewed. First information on chemical properties of Bh was obtained in gas chromatographic experiments on an atom-at-a-time basis. Chemical separation and characterization of 6 atoms of ²⁶⁷Bh produced in the bombardment of a ²⁴⁹Bk target with ²²Ne beams are outlined. Aqueous chemistry of Rf being performed at JAERI (Japan Atomic Energy Research Institute) is briefly summarized. On-line anionexchange experiments in acidic solutions on ²⁶¹Rf produced in the ²⁴⁸Cm (¹⁸O, 5n) reaction were conducted with a rapid ion-exchange separation apparatus. Characteristic anion-exchange behavior of Rf is discussed.

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Tc metal and metal-like carbide phases are revisited with special attention given to Tc-rich phases in the view of prospective nuclear fuel utilization and alternative transmutation targets fabrication. A new Tc-metal phase has been found and new softer conditions for the Tc carbide formation were observed. The unit cell parameters of a new orthorhombic Tc metal were a = 2.805 (4), b = 4.958 (8), c = 4.474 (5) Å (V/z = 15.55ų) for Tc-C with 1.38wt. % C and a = 2.815 (4), b = 4.963 (8), c = 4.482 (5) Å (V/z = 15.65 A³) for Tc-C with 1.96 wt. % C.

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The discrete-variational (DV-X_a) method and Mulliken bond overlap population analyses were performed to study the electronic structure of technetium carbide and clarify the chemical formula Tc₆C proposed for this compound.

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Pertechnetate ion-selective PVC membrane electrodes based on quaternary alkylammonium and phosphonium salts (bromides and pertechnetates) were examined. The most favorable ionophore was tetradecyltrimethylammonium bromide. The response function was linear within the concentration range 10^-2-10^-6 mol/L and the slope was 52 mV/pTcO₄. The detection limit remained at 5·10^-7 mol/L. The selectivity and response time of the electrodes was studied and it was found that the electrodes exhibited high selectivity to TcO₄^--anion against the main inorganic components of radioactive waste solutions and environmental waters (nitrate, sulfate, chloride and others). The electrodes response was stable over a wide pH range.

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Sorption behavior of rhenium with respect to new sorption materials was the object of this study in order to define the possibility of its extraction and concentration from dilute solutions. The sorption materials were prepared by modifying of high-area carbon cloth with a natural biopolymer-chitosan. The three types of sorption materials with different degree of amino groups protonation were obtained. Modified materials have higher sorption capacity as compared to initial carbon cloth. Sorption behavior of the materials was found to be conditioned by the number of the protonated amino groups. We propose that electrostatic interaction of perrhenate ion ReO₄^- with the protonated amino groups -NH₃⁺ takes place.

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Analysis of ⁹⁹Tc using an extraction chromatographic resin to isolate technetium from other elements, followed by liquid scintillation counting has become common worldwide. The method is robust and has been applied to a wide variety of matrix types. Recently, high biases have been reported when samples with high levels of naturally occurring uranium were analyzed. The problem was traced to incomplete decontamination of the technetium fraction from ²³⁴Th (daughter of ²³⁸U) present in the samples. A variety of protocol modifications to the load and rinse solutions were attempted in order to improve the decontamination of the technetium fraction. It was determined that complexing agents were required to remove thorium from the column. Oxalate solutions provided better decontamination than nitric acid and hydrochloric acid solutions alone for samples with low levels of natural uranium. However, fluoride was found to be necessary to ensure adequate decontamination from samples containing up to 44 Bq of natural uranium.

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The distribution of Tc (VII) between aqueous acidic solutions and organic solutions of nitrogen-containing extractants is investigated in order to establish the relationships between extraction power towards the Tc (VII) -anion, ligand molecular structure, influence of the media and the speciation in this ion-pair extraction. Ligands belonging to the class of calixarenes, derivatized with pyridino groups were newly devloped for these purposes. The number of substituents per calixarene, the position of the nitrogen and the size of calixarene are varying structural parameters. The nitrogen atoms are either protonated or quaternized to allow ion-pair extraction. The aqueous phase contains nitrate or chloride at varying or constant ionic strength. Experiments using Aliquat-336 were conductedunder similar conditions.

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The distributions of technetium among solid, liquid and gas phases in supercritical water reactions were investigated for the decomposition process of nonflammable plastic materials contaminated with technetium. In addition to supercritical water (SCW) methods with or without H₂O₂ which have been investigated extensively for decomposition method for the plastics, SCW with RuO₂, developed by us, characteristic of reductive reaction was investigated for technetium distributions. The distributions of technetium were determined by using ^95mTc tracer with or without its carrier ⁹⁹Tc. The gases produced during the decomposition of the organic material contain no radioactivity under all conditions in this study. Also, technetium shows a tendency to transfer to solid phase but not to liquid phase in SCW with RuO₂. These results indicate that this process is suggested as a predominant candidate for the treatment of nonflammable organic materials in low-level radioactive wastes (LLW).

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In order to study the stability of Tc (IV) complexes in chloride media under alpha radiation produced by a cyclotron, an electrochemical cell was developed. In this cell, the stability of TcCl₆^2-, TcCl₅ (H₂O) ^-, Tc₂OCl₁₀^4-, Tc_nO_y ^{(4n-2y) +} and TcO₂. xH₂O were studied in 3 M chloride media with a pH range from 0.3 to 2.5. The stability of a (TcCl₆^2-/TcCl₅ (H₂O) -/Tc₂OCl₁₀^4-) mixture was also investigated during alpha irradiation under a constant current. These studies showed that TcCl₆^2- is a very stable compound whereas chloro-oxygenated compounds were oxidized to Tc (VII). Consequently, the relative stabilities of the Tc (IV) complexes in 3 M chloride media under alpha irradiation was determined.

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Mechanisms of the radiolytic formation of⁹⁹Tc^IVO₂·nH₂O colloids were studied by bremsstrahlung irradiation of an aqueous pertechnetate (Tc^VIIO₄^-) solution under different conditions; pH of the target solution, concentration of TcO₄^- and presence or absence of radical scavengers and of seed particles of TcO₂. nH₂O. Colloid particles (30-130 nm) of TcO₂·nH₂O - a coagulate of nanoparticles with the size of 2 nm - were radiolytically produced at pH higher than 3, whereas a soluble Tc (IV) species but colloid was formed at lower pH. The soluble Tc (IV) species transformed to the TcO₂·nH₂O colloid when the pH of the solution was raised to 3 or higher after the irradiation. This fact suggests that the soluble Tc (IV) species is a precursor of the TcO₂·nH₂O colloid. The presence of TcO₂·nH₂O seed particles in the target solution of TcO₄^- did not enlarge of the partcile size, revealing that the solidification would take place rather in the solution than on the surface of nanoparticles. The reduction of TcO₄^- in acidic solutions proceeded mainly through processes involving a bimolecular reaction of TcO₄^- with hydrogen radicals, followed by the successive disproportionation reactions of Tc (VI) and Tc (V).

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Since ⁹⁸Tc and ⁹⁹Tc decay to ⁹⁸Ru and ⁹⁹Ru, respectively, via the β^- transition, the property of Tc in cosmo- and geochemical fields can be deduced from precise isotopic studies of Ru. Through the approaches on isotopic analyses of Ru in cosmo- and geochemical samples, mass spectrometric techniques with thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICP-MS) and secondary ion mass spectrometry (SIMS) have been effectively used. I report herewith the following three topics about the Ru isotopic studies related with the behavior of Tc in cosmo- and geochemical fields: (1) Initial abundance of Tc in the solar system deduced from the Ru isotopic compositions in meteoritic samples, (2) geochemical behavior of fissiogenic Tc in natural fission reactor zones at the 0klo uranium deposit, and (3) a possibility of cosmic-ray produced Tc in terrestrial molybdenite ore bodies.

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⁹⁹Tc is a β-emitter, E_max = 294 keV, with a very long half-life (T_1/2 = 2.11 × 10⁵ y). It is mainly produced in the fission of ²³⁵U and ²³⁹Pu at a rate of about 6%. This rate together with its long half-life makes it a significant nuclide in the whole nuclear fuel cycle, from which it can be introduced into the environment at different rates depending on the cycle step. A gross estimation shows that adding all the possible sources, at least 2000 TBq had been released into the environment up to 2000 and that up to the middle of the nineties of the last century some 64000 TBq had been produced worldwide. Nuclear explosions have liberated some 160 TBq into the environment. In this work, environmental distribution of ⁹⁹Tc as well as the methods for its determination will be discussed. Emphasis is put on the environmental relevance of ⁹⁹Tc, mainly with regard to the future committed radiation dose received by the population and to the problem of nuclear waste management. Its determination at environmental levels is a challenging task. For that, special mention is made about the mass spectrometric methods for its measurement.

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Technetium-99 is thought to be highly soluble and rarely adsorbed onto soil, however, its mobility under natural environment is not well known because its scarcity and low levels in environmental samples has limited the available data. In this study, we determined ⁹⁹Tc contents in 27 plant samples collected in three forest sites in 1994 and 1995 around the Chernobyl area to obtain transfer factors (TFs) of Tc in the soil-plant system under environmental conditions. The samples were leaves of raspberry, strawberry and pink plants, black alder, birch, cowberry and oak trees, and ferns. After chemical separation, ⁹⁹Tc in the sample was measured by ICP-MS. Tc-95m was used as a yield tracer and the total recovery ranged from 0.48 to 0.92 with an average of 0.76. The determined ⁹⁹Tc concentrations in plants ranged from <0.006 to 6.0 mBq g^-1 (dry weight basis). TF values ranged from <0.006 to 0.47, based on the ⁹⁹Tc contents of the soil organic layers. The highest TF was found in the leaves of raspberry plants. The observed TFs were much lower than the values of 8.1-2600 compiled by IAEA for grass, fodder and leafy vegetables.

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Analytical method for technetium-99 in liquid effluent was investigated and had been applied for measurement of liquid effluents discharged from the Tokai reprocessing plant in Japan. The quarterly averaged concentrations of ⁹⁹Tc in liquid effluents from 1990 to 2000 were ranged from N.D. (<5 × 10^-7 Bq·cm^-3) to 6.7 × 10^-5 Bq·cm^-3. The average of the normalized annual release of ⁹⁹Tc was 7.4 × 10^-4 GBq· (GWa) ^-1 and it was approximately one fiftyfifth of Iodine-129, which was one of the typical nuclides to have difficulty to remove from liquid effluent. The committed effective dose by intake of seaweed was evaluated to be less than 3 × 10^-10 mSv·a^-1.

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Electrolytic reduction of Tc (VII) in a nitric acid solution was examined to recover Tc as well as rare metals (Pd, Ru, and Rh) by an electrolytic extraction method, i. e. electro-reductive deposition, from a spent fuel solution for future nuclear fuel reprocessing. An absorption peak at 482 nm observed after electrolytic reduction of Tc (VII) in 3 M HNO₃ at -0.3 and -1.0V vs SSE (standard silver electrode) suggests the reduction of Tc (VII) to Tc (IV). When Pd is present together with Tc in 1 M HNO₃, the concentration of Tc decreased to 85% of the initial concentration by electrolysis at ±0.0 V vs. SSE for 60 min, suggesting acceleration of Tc deposition by Pd (promoter effect). The Tc concentration, however, increased returning to the initial value after further electrolysis. The Pd deposit from Tc-Pd-Ru-Rh solution redissolved more easily than that from Pd-Ru-Rh, as a consequence of a change in the oxidation-reduction property of the Pd deposit due to the presence of Tc in the solution.

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Tc extraction and separation experiments were performed basing on PUREX technique with using spent UO₂ fuel with burn-up of 44 GWd t^-1. The experimental results were examined with performing calculations by a simulation code ESSCAR (Extraction System Simulation Code for Advanced Reprocessing). It was demonstrated that Tc can be extracted almost quantitatively from a dissolver solution and that extracted Tc also can be recovered almost quantitatively by scrubbing. Further, it is clearly presented with the calculation results of ESSCAR that Tc extraction mechanism is dominated by the synergistic effect of Zr and U.

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A novel reprocessing system with recovery of actinides, long-lived fission products (LLFP) and valuable rare metal fission products (RMFP) has been proposed. This process is based on ion exchange (IX) and catalytic electrolytic extraction (CEE). The pre-filtration step using tertiary pyridine-type anion-exchange resin is set prior to the main actinide recovery steps in this system. The perfect isolation of platinum group elements (Pt-G) such as 106Ru from fuel dissolver solution was successfully demonstrated for irradiated mixed oxide (MOX) fuel. The CEE method, being set as a post-pre-filtration process, was applicable to separation of RMFP including TcO₄^- and ReO₄^- by selective and accelerative deposition with Pd²⁺ as a catalyst. Quaternary Pd-Ru-Rh-Re deposited Pt electrodes showed the highest cathodic current. The catalytic ability is about twice superior to that of the base Pt electrode when used for artificial sea water as well as alkaline solution. The recovery and separation of actinides and RMFP by a multi-functional reprocessing system consisting of IX and CEE will minimize the quantity and improve the quality of high level liquid waste (HLLW). The recovered RMFP will be used as a “FP-catalyst” for hydrogen production in water electrolysis.

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The present study examines the potential for the demonstration of fission product transmutation in the experimental fast reactor JOYO at JNC's Oarai Engineering Center. The possibility of creating a highly-efficient transmutation irradiation field of JOYO by loading neutron moderating subassemblies in the reflector region was investigated in a series of scoping calculations. A cluster of reflector subassemblies was replaced with beryllium or zirconium hydride (ZrH_1.65) moderated subassemblies. These moderated subassemblies surrounded one central test subassembly that would contain ⁹⁹Tc or ¹²⁹I target material. With this modification, a high fast neutron flux can be tailored to epithermal or thermal energies. A comparison of reaction rates among the spectra is made illustrating the integral effects on selected target reactions. The ⁹⁹Tc transmutation rate achieved was 21.0% using ZrH_1.65 and 27.8% using beryllium as moderator. As a result of this study, basic characteristics of LLFP transmutation in JOYO using relevant moderator materials were clarified and the future feasibility was shown.

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An account is given of a series of study to accurately determine the cross section of the ⁹⁹Tc (n, γ) ¹⁰⁰Tc reaction for thermal neutrons. Methods used are an activation analysis in which γ rays in ¹⁰⁰Ru are examined, and analyses of ground-state transitions in ¹⁰⁰Tc. To reduce uncertainty of the cross section obtained in the activation measurement, an attempt was made to accurately determine emission probabilities of γrays in ¹⁰⁰Ru.

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In the context of the French nuclear waste management act of 1991, two options have been considered following enhanced reprocessing of spent fuel. The reference option is the transmutation by neutronic bombardment, the second option is to immobilize the separated radiotoxic elements in dedicated matrices ensuring long term stability. This paper summarizes the research and development activities carried out by CEA in France, concerning technetium. Nearly 90% of the technetium-99 present in spent fuel is separated in the UP2-800 reprocessing plant at La Hague, producing about 900 kg of Tc each year. The first part of the paper deals with the irradiation experiment ANTICORP 1 which aims at transmuting ⁹⁹Tc under the form of metallic rods, in the core of the Phénix reactor. The goal of ANTICORP 1 is to achieve a transmutation rate of ⁹⁹Tc in ¹⁰⁰Ru greater than 20%. The main options chosen for the design and the safety study of the experiment are described. In addition, the planning of the irradiation and the post-irradiation exams foreseen, are detailed. The second part of the paper describes the studies carried out to investigate technetium metal as a potential containment matrix. The corrosion rate of this metal under water was measured over one year of alteration at 25°C.

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