The Study of (<Emphasis Type="Italic">n,d</Emphasis>) Reaction Cross Sections for Some Medium Weight Targets up to 30 MeV

In this study, neutron incident reaction cross sections for some medium target nuclei ( ⁴⁴ Ca, ⁶⁵ Cu, ⁵⁴ Fe, ⁵⁶ Fe, ⁵⁷ Fe, ⁵⁸ Ni, ⁶⁰ Ni and ⁶⁷ Zn) have been investigated for the (n,d) reaction cross sections. These new calculations on the excitation functions of ⁴⁴ Ca(n,d) ⁴³ K, ⁶⁵ Cu(n,d) ⁴⁴ Ni, ⁵⁴ Fe(n,d) ⁵³ Mn, ⁵⁶ Fe(n,d) ⁵⁵ Mn, ⁵⁷ Fe(n,d) ⁵⁶ Mn, ⁵⁸ Ni(n,d) ⁵⁷ Co, ⁶⁰ Ni(n,d) ⁵⁹ Co and ⁶⁷ Zn(n,d) ⁶⁶ Cu reactions have been carried out up to 30 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The PEQ calculations involve the new evaluated the Geometry Dependent Hybrid model. Equilibrium effects are calculated according to the Weisskopf–Ewing model. By using the new cross sections formulae for (n,d) reactions developed by Aydin et al., the obtained results have been discussed and compared with the available experimental data taken from EXFOR database.     

Analysis and evaluation of thermal and resonance neutron activation data

A generalized least-squares technique has been applied to produce a consistent set of thermal and epithermal neutron activation data for the following 20 nuclides produced by neutron capture: ⁴⁶Sc, ⁵¹Ti, ⁵¹Cr, ⁵²V, ⁵⁶Mn, ⁵⁹Fe, ⁶⁰Co, ⁷⁵Se, ⁸⁶Rb, ⁹⁵Zr, ⁹⁷Zr, ¹²⁴Sb, ¹³¹Ba, ¹³⁴Cs, ¹⁴⁰La, ¹⁴¹Ce, ¹⁶⁰Tb, ¹⁸¹Hf, ¹⁸²Ta and ¹⁹⁸Au. The technique combines available information on nuclear data from the literature with measured activation data irradiated in nine reactor positions in Germany, the U.K. and Japan.Most of the solution nuclear data showed a distinct improvement, some by a large amount. These have been compared with the most recent evaluation.     

Radiative rates and electron impact excitation rate coefficients for Ne-like selenium, Se XXV

In this article we report calculations of energy levels, radiative rates, electron impact collision strengths, and effective collision strengths for transitions among the 241 fine-structure levels arising from 2l⁸ and 2l⁷n^′l^′ (n^′≤6 and l^′≤n^′−1) configurations of Ne-like Se XXV using the Flexible Atomic Code. Energy levels and radiative rates are calculated within the relativistic configuration-interaction method. Direct excitation collision strengths are calculated using the relativistic distorted-wave approximation and high-energy collision strengths are obtained in the relativistic plane-wave approximation. Resonance contributions through the relevant Na-like doubly-excited configurations 2l⁷n^′l^′n^″l^″ (3≤n^′≤7, l^′≤n^′−1, n^′≤n^″≤50, and l^″≤8) are explicitly taken into account via the independent-process and isolated-resonance approximation using distorted waves. Resonant stabilizing transitions and possibly important radiative decays from the resonances toward low-lying autoionizing levels are considered. In addition, the resonance contributions from Na-like 2l⁶3l^′3l^″n^?l^? (n^?=3−6) configurations are included and found to be predominant for many transitions among the singly-excited states in Ne-like Se XXV. We present the radiative rates, oscillator strengths, and line strengths for all electric dipole, magnetic dipole, electric quadrupole, magnetic quadrupole, electric octopole, and magnetic octopole transitions among the 241 levels. The effective collision strengths are reported for all 28920 transitions among the 241 levels over a wide temperature range up to 10 keV. To assess the reliability and accuracy of the present collisional data, we have performed a 27-state close-coupling calculation, employing the Dirac R-matrix theory. The results from the close-coupling calculation and the independent-process calculation for the identical target states are found to be in good agreement.     

Effect of temperature on studtite stability: Thermogravimetry and differential scanning calorimetry investigations

The main objective of this work is the study of the influence of temperature on the stability of the uranyl peroxide tetrahydrate (UO₂O₂ · 4H₂O) studtite, which may form on the spent nuclear fuel surface as a secondary solid phase. Preliminary results on the synthesis of studtite in the laboratory at different temperatures have shown that the solid phases formed when mixing hydrogen peroxide and uranyl nitrate depends on temperature. Studtite is obtained at 298 K, meta-studtite (UO₂O₂ · 2H₂O) at 373 K, and meta-schoepite (UO₃ · nH₂O, with n < 2) at 423 K. Because of the temperature effect on the stability of uranyl peroxides, a thermogravimetric (TG) study of studtite has been performed. The main results obtained are that three transformations occur depending on temperature. At 403 K, studtite transforms to meta-studtite, at 504 K, meta-studtite transforms to meta-schoepite, and, finally, at 840 K, meta-schoepite transforms to U₃O₈. By means of the differential scanning calorimetry the molar enthalpies of the transformations occurring at 403 and 504 K have been determined to be −42 ± 10 and −46 ± 2 kJ mol⁻¹, respectively.     

Electron impact collision strengths and oscillator strengths for Ge-, Ga-, Zn-, Cu-, Ni-, and Co-like Au ions

Energy levels, oscillator strengths, and electron impact collision strengths have been calculated for Ge-, Ga-, Zn-, Cu-, Ni-, and Co-like Au ions. For Ni-like Au, these atomic data are obtained among the levels belonging to the configurations of ([Ne])3s²3p⁶3d¹⁰, 3s²3p⁶3d⁹nl, 3s²3p⁵3d¹⁰nl, and 3s 3p⁶3d¹⁰nl (n = 4, 5; l = 0, 1, … , n − 1). For other Au ions, more levels have been obtained with special attention to atomic data up to transitions of 5f → 3d for emission or 3d → 5f for absorption. Configuration interactions are taken into account for all levels included. Collision strengths have been obtained at 20 scattered electron energies (5-40,000 eV) and they are listed at six representative energies of 100, 500, 1000, 5000, 10,000, and 20,000 eV in this work. Effective collision strengths have been obtained by assuming a Maxwellian electron velocity distribution at 10 representative temperatures ranging from 500 to 5000 eV. The present dataset should be adequate for most applications. The energy levels are expected to be accurate to within 0.5%, while oscillator strengths and collision strengths for strong transitions are probably accurate to better than 20%. The complete dataset is available electronically from http://www.astronomy.csdb.cn/EIE/.     

Atomic data and spectral line intensities for Ni XVII

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XVII. We include in the calculations the 23 lowest configurations, corresponding to 159 fine-structure levels: 3l3l′, 3l4l″, and 3s5l?, with l, l′ = s, p, d, l″ = s, p, d, f, and l? = s, p, d. Collision strengths are calculated at five incident energies for all transitions at varying energies above the threshold of each transition. One additional energy, very close to the threshold of each transition, has also been included. Calculations have been carried out using the Flexible Atomic Code in the distorted wave approximation. Additional calculations have been performed with the University College London suite of codes for comparison. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10⁸ − 10¹⁴ cm⁻³ and at an electron temperature of log T_e(K) = 6.5, corresponding to the maximum abundance of Ni XVII. Spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.     

Wavelengths and transition probabilities for n = 4 → n′ = 4 transitions in heavy Cu-like ions (70 ? Z ? 92)

Wavelengths and transition probabilities have been calculated for the n = 4 → n′ = 4 allowed transitions in the heavy Cu-like ions with Z = 70-92. Fully relativistic multiconfiguration Dirac-Fock (MCDF) calculations were carried out. They take into account the correlations within the n = 4 complex, the core-valence n = 3 → n′ = 4 virtual excitations, and quantum electrodynamics effects. The present results are compared to and agree well with recent electron-beam ion-trap (EBIT) measurements in ytterbium, tungsten, osmium, gold, lead, bismuth, thorium, and uranium.     

Ion irradiation induced nanocrystal formation in amorphous Zr55Cu30Al10Ni5 alloy

Ion irradiation can be used to induce partial crystallization in metallic glasses to improve their surface properties. We investigated the microstructural changes in ribbon Zr₅₅Cu₃₀Al₁₀Ni₅ metallic glass after 1 MeV Cu-ion irradiation at room temperature, to a fluence of 1.0 × 10¹⁶ cm⁻². In contrast to a recent report by others that there was no irradiation induced crystallization in the same alloy [S. Nagata, S. Higashi, B. Tsuchiya, K. Toh, T. Shikama, K. Takahiro, K. Ozaki, K. Kawatusra, S. Yamamoto, A. Inouye, Nucl. Instr. and Meth. B 257 (2007) 420], we have observed nanocrystals in the as-irradiated samples. Two groups of nanocrystals, one with diameters of 5–10 nm and another with diameters of 50–100 nm are observed by using high resolution transmission electron microscopy. Experimentally measured planar spacings (d-values) agree with the expectations for Cu₁₀Zr₇, NiZr₂ and CuZr₂ phases. We further discussed the possibility to form a substitutional intermetallic (Ni_xCu_1−x)Zr₂ phase.     

Nuclear data sheets for A = 136

The 1961 version of Nuclear Data Sheets for A = 136 has been revised according to experimental data received before September 1, 1973. Selected experimental data, discussions for J^π-assignments, and detailed level schemes are presented.Additional data now detail the decays of ¹³⁶Te, ¹³⁶Pm, and ¹³⁶Nd, and the level structure for ¹³⁶Xe, ¹³⁶Ba, ¹³⁶Ce, ¹³⁶Pr, and ¹³⁶Nd are improved significantly. The low-lying levels in ¹³⁶Ba are very well established. Additional information on the higher excitations in ¹³⁶Ba is needed, possibly through more definitive ¹³⁵Ba(n,γ)¹³⁶Ba experiments. The relative positions of the isomers in ¹³⁶I and the details of the level structure for ¹³⁶La and ¹³⁶Cs are still unknown. Areas of continuing experimental interest are the decays of ^136mI, ¹³⁶Nd, ¹³⁶Pm, and the quasirotational levels of ¹³⁶Ce and ¹³⁶Nd. The level structure of ¹³⁶Xe(¹³⁶Pr) will be subject to major additions (complete revision) in the near future. These new decay data were not included in this evaluation because of their preliminary nature.     

Effect of oxygen potential on the sintering behavior of MgO-based heterogeneous fuels containing (Pu, Am)O2−x

The effect of oxygen potential on the sintering behavior of MgO-based heterogeneous fuels containing (Pu, Am)O_2−x was experimentally investigated. Sintering tests in various atmospheres, i.e. air, moisturized 4%H₂-Ar, and 4%H₂-Ar atmosphere, were carried out. The sintering behavior was found to be significantly affected by the oxygen potential in the sintering atmosphere. The sintered density decreased with decreasing oxygen potential. The (Pu, Am)O_2−x phase sintered in a reductive atmosphere had hypostoichiometry. The aggregates of the (Pu, Am)O_2−x phase sintered in the reductive atmosphere grew, in comparison with those in the oxidizing one. The sintering mechanism was discussed in terms of the difference in sintering behavior of (Pu, Am)O_2−x and MgO.     

Calculation of Excitation Function of Some Structural Fusion Material for (n, p) Reactions up to 25 MeV

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, Furthermore, there are not radioactive nuclear waste problems in the fusion reactors. In this study, (n, p) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn and ⁵⁶Fe have been investigated. The new calculations on the excitation functions of ²⁷ Al(n, p) ²⁷ Mg, ⁵¹ V(n, p) ⁵¹ Ti, ⁵² Cr(n, p) ⁵² V, ⁵⁵ Mn(n, p) ⁵⁵ Cr and ⁵⁶ Fe(n, p) ⁵⁶ Mn reactions have been carried out up to 30 MeV incident neutron energy. Statistical model calculations, based on the Hauser–Feshbach formalism, have been carried out using the TALYS-1.0 and were compared with available experimental data in the literature and with ENDF/B-VII, T = 300 K; JENDL-3.3, T = 300 K and JEFF-3.1, T = 300 K evaluated libraries.     

Excitation functions of Ir formed in proton-induced reactions on highly enriched Os up to 66 MeV

Cross sections of proton-induced nuclear reactions on highly enriched ¹⁹²Os were measured up to 66 MeV by using the stacked-foil irradiation technique. Excitation functions are presented for the reactions ¹⁹²Os(p,n)¹⁹²Ir, ¹⁹²Os(p,3n)¹⁹⁰Ir, ¹⁹²Os(p,4n)¹⁸⁹Ir, ¹⁹²Os(p,5n)¹⁸⁸Ir, ¹⁹²Os(p,6n)¹⁸⁷Ir and ¹⁹²Os(p,7n)¹⁸⁶Ir. No earlier experimental cross-section data could be found in the literature except for the ¹⁹²Os(p,n)¹⁹²Ir process. Our new experimental results are compared with theoretical predictions by means of the theoretical model code ALICE/ASH. Integral thick-target yield calculations were also performed for the ¹⁹²Os(p,n)¹⁹²Ir and ¹⁹²Os(p,3n)¹⁹⁰Ir reactions to evaluate the ¹⁹⁰Ir contamination level, as a function of energy, in the case of ¹⁹²Ir productions.     

Cross-section measurements for (n, 2n), (n,p) and (n, α) reactions on strontium isotopes at the neutron energy about 14 MeV

Cross-sections for ⁸⁴Sr(n, 2n)⁸³Sr, ⁸⁶Sr(n, 2n)^85mSr, ⁸⁶Sr(n, 2n)⁸⁵Sr, ⁸⁸Sr(n, 2n)^87mSr, ⁸⁴Sr(n, p)⁸⁴Rb, ⁸⁶Sr(n, p)⁸⁶Rb, ⁸⁸Sr(n, p)⁸⁸Rb and ⁸⁸Sr(n, α)^85mKr reactions have been measured at neutron energies from 13.5 to 14.6 MeV using activation technique and by means of γ-ray spectrometry. The neutron flux was determined using the monitor reaction ⁹³Nb(n, 2n)^92mNb and the neutron energies were measured by the method of cross-section ratios for ⁹⁰Zr(n, 2n)⁸⁹Zr to ⁹³Nb (n, 2n)^92mNb reactions. The results of present work are compared with data published previously.     

On the radiolysis of iodide, nitrate and nitrite ions in aqueous solution: An experimental and modelling study

High radiation fields are predicted in the atmospheres in the reactor containment under postulated severe accident conditions. In particular, an experimental and modelling project (PARIS) has provided results, which show that nitrogen dioxide was the dominant measured species at high doses (>1 kGy) in air/steam mixtures. In addition, nitrite and nitrate ions were measured in the post-test containment sumps in some Phebus FP in-reactor integral experiments; but their separate effects on iodine volatility from irradiated aqueous solutions of iodide using appear unreported in open literature.To address this issue, this paper presents an overview of the results of an experimental and modelling study carried out at PSI, Switzerland. The experimental study consisted of small-scale irradiations of CsI, boric acid and tracer containing aqueous solutions. Tests were first carried out without nitrate or nitrite ions to obtain results to confirm expected iodine behaviour by correlation with predicted results, which were generated by concurrently developed code (PSIodine). The solutions were sparged with N₂O, argon and air to provide different net oxidation systems and to remove volatile iodine for measurement. Since the radiation chemistry of N₂O-saturated iodide solutions is well established and the measured I₂ yields and final pH correlate very well with the PSIodine code predictions, the effect of added nitrite ions to these solutions has provided results, which support the correct choice of relevant reactions for inclusion in the nitrate-model.Both experimental and predicted results clearly show that nitrate or nitrite ions in argon-sparged and irradiated iodide solutions (conc., 10⁻⁴ mol dm⁻³) containing boric acid lower % I₂ yields up to an initial NO₃⁻ concentration of ∼5.0 × 10⁻³ mol dm⁻³. Using a low CsI concentration (4.0 × 10⁻⁵ mol dm⁻³) estimated in containment sump during a postulated severe-accident, an initial nitrate concentration (10⁻³ mol dm⁻³) and pH 7.1, ∼3.6% I₂ was produced by argon sparging at a dose of 20.5 kGy. In contrast, 80% I₂ was formed at a dose of 12 kGy in the absence of nitrate ions.Irradiated and air-sparged CsI solutions, due to the lower net oxidation, gave the expected lower % I₂ yields than their argon-sparged counterparts. However, the reduction of volatile iodine species by radiation products of nitrate ions was enhanced. For example, using CsI solutions (conc., 10⁻⁴ mol dm⁻³), initial pH 4.6 and a range of nitrate ion concentrations (0, 10⁻⁴, 10⁻³ and 10⁻² mol dm⁻³), the % I₂ yields at a dose of 2 kGy have lowered from 26.9% to 25.6%, 3.2% and 2.8%, respectively. In the latter experiment, only ∼6% I₂ at a dose of ∼20 kGy was produced. In the absence of nitrate ions, a yield of ∼93% I₂ at only 5 kGy dose was obtained. By comparison, the % I₂ yields from their Ar-sparged counterpart experiments were lowered from ∼88% to ∼72%, 11% and 22% in the same nitrate concentration range. Therefore, apart from the lower net oxidation in O₂-containing solutions, the results indicate that the reduction of volatile iodine species by products of nitrate ion irradiation is enhanced in the presence of dissolved O₂.     

Defects creation in sapphire by swift heavy ions: A fluence depending process

Single crystals of sapphire (α-Al₂O₃) were irradiated at GANIL with 0.7 MeV/amu xenon ions corresponding to an electronic stopping power of 21 keV/nm. Several fluences were applied between 5 × 10¹¹ and 2 × 10¹⁴ ions/cm². Irradiated samples were characterized using optical absorption spectroscopy. This technique exhibited the characteristic bands associated with F and F⁺ centers defects. The F centers density was found to increase with the fluence following two different kinetics: a rapid increase for fluences less than 10¹³ ions/cm² and then, a slow increase for higher fluences. For fluences less than 10¹³ ions/cm², results are in good agreement with those obtained by Canut et al. [B. Canut, A. Benyagoub, G. Marest, A. Meftah, N. Moncoffre, S.M.M. Ramos, F. Studer, P. Thévenard, M. Toulemonde, Phys. Rev. B 51 (1995) 12194]. In the fluences range: 10¹³-10¹⁴ ions/cm², the F centers defects creation process is found to be different from the one evidenced for fluences less than 10¹³ ions/cm².     

Nuclear Data Sheets for A = 71

The evaluated spectroscopic data are presented for experimentally known nuclides of mass 71 (Mn,Fe,Co,Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr). Excited-state data are nonexistent for ⁷¹Mn, ⁷¹Fe, ⁷¹Co and ⁷¹Kr. Significant new data have been added since the last evaluation of A=71 nuclides by M. Bhat (1993Bh02). Excited states are now known in ⁷¹Ni and ⁷¹Cu, and enhanced information about high-spin excitations is available for ⁷¹Ga, ⁷¹As and ⁷¹Br. The decay schemes of radioactive isotopes ⁷¹Mn and ⁷¹Fe are not known at all, and those for ⁷¹Co, ^71mNi and ⁷¹Kr are not known well. For the decay of ⁷¹Cu, ^71gNi, and ⁷¹Br, extensive data are available, but in the opinion of the evaluators the decay schemes still seem incomplete.This work supersedes earlier full evaluations of A=71 published by 1988Bh01, 1979Ke06 and 1973Al33, and the last one published in ‘update’ mode by 1993Bh02.     

Oxygen glow discharge experiment to remove deposited layers and to release trapped hydrogen isotopes in HT-7 superconducting tokamak

An experiment to remove re-deposited layers and to release hydrogen using a glow discharge in oxygen (O-GDC) has been performed in the HT-7 superconducting tokamak. In the absence of magnetic fields, the O-GDC wall conditioning had produced rapid, controlled co-deposit removal. Average removal rates, 5.2 × 10²² H-atoms/h, 5.65 × 10²¹ D-atoms/h and 5.53 × 10²² C-atoms/h, respectively, were obtained during 145 min O-GDC experiment in the pressure range 0.5-1.5 Pa. The corresponding removal rate of co-deposited films was ∼1.19 μm/day (26.5 g/day for carbon) based on an area of 12 m². Compared to thermo-oxidation and O-ICR experiment, high pressure O-GDC wall conditioning promoted the oxidation and improved the C and D atoms removal. In the O-GDC experiment, the removal rates of H-atoms and D-atoms as H₂O, HDO and D₂O were higher than that of H₂ and D₂ by factors of about 20 and 50, respectively. During the 145 min O-GDC experiment, about 14.5% O-atoms were converted into carbon oxides and hydroxides, and about 5.37 × 10²² O-atoms were adsorbed on the walls corresponding to a coverage of 4.5 × 10²¹ O/m² on an wall area of 12 m². In a 100 min helium glow discharge (He-GDC) following the O-GDC experiment, 1.53 × 10²² O-atoms, about 28.5% oxygen retained on the walls, were removed. The removal rate of H-atoms in He-GDC cleaning after O-GDC experiment was lower than that in He-GDC cleaning before O-GDC experiment, which indicates that the O-GDC wall conditioning had effectively reduced hydrogen retention on the walls.     

Evaluation of the specific radioactivity of 40 elements created by nuclear transmutation of fission products

A burnup calculation was performed to analyze Après ORIENT process which aims at creating highly-valuable elements by nuclear transmutation of fission products (FPs) separated from LWR spent nuclear fuels. In this paper, numerical evaluation of the specific radioactivity of 40 created elements, from reloaded each FP element, with atomic number from 31 to 70 at the end of the time of 5-year-cooling after the irradiation for 1125 days in each LWR and FBR was carried out. These 40 created elements were classified in 6 categories according to levels of the specific radioactivity and the length of additional cooling period, which was needed for the specific radioactivity to decrease below the exemption level defined by International Atomic Energy Agency. As a result, created ₃₁Ga, ₃₂Ge, ₃₃As, ₃₅Br, ₆₈Er, and ₇₀Yb did not contain any radioisotopes at the end of the 5-year-cooling. It should be noted that created ₃₇Rb, ₅₇La, and ₆₀Nd had much lower specific radioactivities than natural composition of them. Moreover, specific radioactivities of created ₄₀Zr, ₄₂Mo, ₄₄Ru, ₄₆Pd, ₄₉In, and ₅₄Xe were sufficiently lower than their exemption levels at the end of the 5-year-cooling. On the other hand, created ₃₉Y, ₄₅Rh, ₅₀Sn, ₅₂Te, ₅₈Ce, ₅₉Pr, ₆₅Tb, and ₆₆Dy needed additional cooling period less than 10 years until their specific radioactivities decreased below their exemption levels. Then, each additional cooling period required for created ₄₈Cd, ₅₁Sb, ₆₄Gd, and ₆₉Tm was estimated at 10–100 years. Additionally, specific radioactivities of other 13 created elements would not decrease below their exemption levels even if they had been stored for 100 years. There could be significance to create important elements as resources classified in first 4 of the 6 categories defined in this paper, by nuclear transmutation of fission products. In consideration of the efficiency of creation, the radioactivity, and the importance as resources of each product, ₄₄Ru, ₄₆Pd, ₅₂Te, ₆₀Nd, and ₆₆Dy were specially selected as the most important created elements to be more researched in the future Après ORIENT program.     

Relativistic energy contributions to the N = 2 triplet levels in helium-like ions

The 1s2s³S?1s2p³P_J (J = 0, 1, 2) transitions in helium-like ions can be used to test QED, but only if the other contributions to the transition energy, and especially the relativistic contributions are known to high accuracy.This work tests the relativistic calculations by comparing the theoretical ${}^3\text{P}{}_{\mathrm{J}}$ splittings (which are nearly ndependent of QED) with each other and with experiment. An estimate of the largest uncalculated relativistic term, of relative order α⁴Z⁴, is also made.It is found that the calculations of Hata and Grant are not very accurate, and that the small discrepancy between Drake and experiment vanishes if the α⁴Z⁴ relativistic term is included.     

Leach testing at 50 °C of α-doped SON68 glass alteration gels

Gels formed by altering α-doped (Np, Pu, Am) SON68 glass at 300 °C were leached during 1 year at 44 cm⁻¹ and 50 °C under oxidizing conditions (Eh_/NHE ≈ +150 mV) and under reducing conditions (Eh_/NHE ≈ −250 mV). After 3 days of leaching the gel dissolution was highly incongruent. The gel dissolution rate calculated from the silicon concentrations was 4.4 × 10⁻⁵ g m⁻² d⁻¹, except for the Am-doped gel, for which the rate was two times higher. During leaching, Np is weakly retained in the gel (35% under oxidizing conditions and 50% under reducing conditions) whereas Pu and Am are strongly retained (over 90%). The three lanthanides La, Ce, and Nd exhibit exactly the same leaching behavior, but different from that of actinides. Speciation and complexation calculations for neodymium showed that its solubility could be controlled by Nd(OH)₃ for periods beyond 3 months. Conversely, no simple chemical compound appears to control the solubility of the actinides.