Mass Spectrometric Study of Ions Formed from Cesium Metaborate Vapor under Electron Impact

An ionization behavior of cesium metaborate vapor under electron impact has been studied by a mass spectrometric method. Formations of Cs²⁺, CsB⁺, CsO⁺, Cs⁺ ₂, Cs₂O⁺, B⁺ and BO^? ₂ ions have been identified in addition to the well known ions of Cs⁺, CsBO⁺, CsBO⁺ ₂ and Cs₂BO⁺ ₂. Ionization processes and vapor precursors for these ions have been given from ionization efficiency curves, appearance energies, temperature dependence of ion intensities and energetics of the ionization processes as follows: the process for the formations of Cs⁺ with AE(Cs⁺)=3.9± 1.0 eV and BO^? ₂ ions is the ion pair formation from CsBO₂(g), that for CsBO⁺ ₂ ion is the simple ionization of CsBO₂(g), that for Cs⁺ with AE (Cs⁺) =9.1±0.5 eV, Cs²⁺, CsBO⁺, CsB⁺, CsO⁺ and B⁺ ions is the dissociative ionization from CsBO₂(g) and that for Cs⁺ ₂, Cs₂O⁺ and Cs₂BO⁺ ₂ ions is the dissociative ionization from Cs₂(BO₂)₂(g). The knowledge of the ionization behavior of cesium metaborate vapor under electron impact is very useful in the mass spectrometric study of vaporization behaviors of CsBO₂(s) and simulated radioactive waste borosilicate glasses.     

Vaporisation thermodynamics of caesium iodide and caesium chromate

Vaporisation studies over solid and liquid CsI have been carried out by Knudsen effusion (753 – 897 K) transpiration (862 – 1125 K) and boiling temperature (977 – 1430 K) methods. The Knudsen mass loss and transpiration data over CsI(s) are consistent with the presence of monomeric species upto 873 K and the vapour pressure values can be represented by the equation: log₁₀P(kPa) = (7.59 ± 0.12) ? 0.00113 T(K) ? (10301 ± 95)/T(K) ? 21088/T²(K) + 1.13 log₁₀T(K) Transpiration and boiling temperature data were used to calculate partial pressures of monomeric (p₁°) and dimeric (p₂°) species over CsI(1) and the values obtained can be represented by the following equations: log₁₀P₁°(kPa) = (19.67 ± 0.38) ? (9628 ± 344)T(K) ? 3.65 log₁₀T(K)log₁₀P₂°(kPa) = (28.42 ± 0.41) ? (9986 ± 415)T(K) ? 6.56 log₁₀T(K) Vapour pressure of Cs₂CrO₄(1) was measured in the temperature range 1225 to 1405 K by transpiration method and vapour pressure calculated assuming monomeric species can be represented by the equation: log₁₀p(kPa) = (8.32 ± 0.26) ? (13434 ± 344)T(K)     

New Phase Transitions in Non-Stoichiometric U3O8-x at High Temperatures, (II)

Electrical conductivity and X-ray diffraction studies on non-stoichiometric U₃O_8-x phase were carried out simultaneously in the range 765°≦T≦995°C and 10^?4≦Po₂≦1 atm. The plot of logσ vs. logPo₂ showed many refractions which corresponded with the phase transitions determined by thermogravimetry reported in the preceding paper. Based on the data of both electrical conductivity and thermogravimetry, the non-stoichiometric defect structures of various U₃O_8-x phases are interpreted as consisting of singly charged oxygen interstitials (O_l′) and doubly charged oxygen vacancies (Vo^.)? Some of the X-ray diffraction lines were found to undergo splitting with decreasing oxygen partial pressure. These splits are qualitatively discussed in reference to the out-of-step structure model. The mechanism of electrical conduction in the high temperature hexagonal U₃O_8-x phases is surmised to be the hopping of small polarons.     

Vaporization study on UO2 and (U1−yNby)O2+x by mass-spectrometric method

The vapor pressures over UO_2.000 and (U_1?yNb_y)O_2+x (y = 0.01, 0.05, x = 0.000–0.022) were measured by the mass-spectrometric method in the temperature range 2025–2343 K. The main gas species over UO_2.000 were observed to be UO₃(g) and UO₂(g) and those over (U_1?yNb_y)O_2+x were NbO₂(g), NbO(g), UO₃(g) and UO₂(g). The partial vapor pressures of almost all gas species over (U_1?yNb_y)O_2+x increased with increasing O/M (M = U + Nb) ratio. With increasing Nb content in (U_1?yNb_y)O_2.000, the partial vapor pressures of UO₂(g) and UO₃(g) decreased and those of NbO(g) and NbO₂(g) increased. The congruently vaporizing composition in the (U_1?yNb_y)O_2+x phase was estimated to be ($\text{U}{}_{\mathrm{0.985\pm 0.005}}\text{Nb}{}_{\mathrm{0.015\pm 0.005}}\text{)O}{}_{2.000}$ from the compositional dependence of the total vapor pressures. The partial molar enthalpy and entropy of oxygen of (U_1?yNb_y)O_2+x calculated from the partial pressures of gaseous species NbO₂(g) and NbO(g) were in fairly good agreement with those previously obtained by the present authors with a thermobalance.     

Volatilization of Technetium from Simulated Reprocessing Solutions

Volatilization behavior of technetium was investigated in order to evaluate the decontamination efficiency of an evaporator for reprocessing waste solutions. The gaseous species of technetium volatilized over HTcO₄ solutions had been considered as the mixture of Tc₂O₇ and HTcO₄. Estimation of the decontamination efficiency needs to determine whether the dominant gaseous species is Tc₂O₇ or HTcO₄. The continuous distillation of dilute HTcO₄ solution was carried out and we obtained the purification factor (PF) defined as the concentration ratio of technetium in the concentrate and distillate. The PF was normalized by total pressure, HTcO₄ molarity and mole number in 1l solution. The normalized PF was reciprocal to the second power of HTcO₄ molarity and was proportional to the activity of water. These findings suggested the dominant gaseous species were Tc₂O₇ and volatilization was the dehydration of HTcO₄ forming gaseous Tc₂O₇. The vapor pressure of Tc₂O₇ was obtained from PF and the equilibrium constant of volatilization reaction was calculated considering that the gaseous species was dominantly Tc₂O₇. The thermodynamic functions controlling the volatilization reaction were obtained from the dependence of equilibrium constant on temperature as, ΔH=82.3 kJ·mol^?1 and ΔS=205.4 J·mol^?1·K^?1, respectively.     

Vaporization of solid lithium nitride

The vaporization of solid lithium nitride has been studied by a mass spectrometric Knudsen effusion method. The solid was found to vaporize congruently to Li(g), Li₂(g) and N₂(g), and partial pressures of them may be represented by the equations: logp_Li (Pa) = (11.487 ± 0.102) ? (9.670 ± 0.081) 10³/T, logp_Li2 (Pa) = (14.306 ± 0.209) ? (14.090 ± 0.166) 10³/T and logp_N2 (Pa) = (10.959 ± 0.157) ? (9.638 ± 0.124) 10³/T in the temperature range 739–859 K. No identification of LiN(g) was made. From the combination of the determined enthalpy of the reaction Li₃N(c) = 3Li(g) + 0.5N₂(g) with appropriate literature data, the enthalpy ΔH°_f298, the free energy ΔG°_f298 and the entropy ΔS°_f298 of formation for solid lithium nitride have been obtained to be (?171.3 ± 7.7) kJ/mol, (?135.4 ± 7.7) kJ/mol and (?120.4 ± 36.5) J/mol · K, respectively.     

Mass-spectrometric study of the vaporization of Li2O(s) and thermochemistry of gaseous LiO,Li2O,Li3O,and Li2O2

The equilibrium vapor pressures over solid lithium oxide (Li₂O) have been measured mass-spectrometrically using platinum Knudsen cells in the temperature range 1300–1700 K. From the gaseous equilibria the heats of formation of LiO(g), Li₂O(g), Li₃O(g), and Li₂O₂(g) were determined as follows: ΔH⁰₀(LiO) = 8.3 ± 3.3 kcal/mol, ΔH⁰₀(Li₂O) = − 42.3 ± 1.1 kcal/mol, ΔH⁰₀(Li₃O) = −48.4 ± 5.6 kcal/mol, and ΔH⁰₀(Li₂O₂) = −71.5 ± 7.4 kcal/mol. The atomization energies are D⁰₀D⁰₀(LiO) = 89.2 ± 3.3 kcal/mol, D⁰₀(Li₂O) = 178.3 ± 1.1 kcal/mol, D⁰₀(Li₃O) = 222.9 ± 5.6 kcal/mol, and D⁰₀(Li₂O₂) = 266.5 ± 7.4 kcal/mol. The relation D⁰₀(LiO) = D⁰₀(Li-OLi) is derived here. The bond dissociation energy D⁰₀(Li-Li₂O) is 44.6 ± 5.5 kcal/mol.In addition, the vaporization of Li₂O has been studied by using molybdenum, tantalum and graphite Knudsen cells in the temperature range 1200–1500 K to measure the distribution of the partial pressures under these conditions. It was found, for example, that due to the reaction of Li₂O with the wall of a molybdenum cell, their partial pressure of Li₃O, which was detected as a stable molecule for the first time, was increased by about a factor of 10 compared with its pressure measured in a platinum cell.     

Detritiation of Glovebox Atmosphere by Using Compact Tritium Removal Equipment

A compact tritium removal equipment (TRE), assembled in a console with casters, has been developed for detritiation of air in a glovebox used for handling of several curies of tritium. The TRE was designed to remove gaseous tritium in the form of T₂, HT and CH₃T through oxidation with precious metal/alumina catalysts followed by adsorption on zeolite pellets.

From the detritiation experiments with hydrogen tritide (HT, 2–20 mCi), the TRE was confirmed to have sufficient performance for the practical use. The tritium concentration in the test gas (total volume –32l; 1%H₂, 5%O₂, 94%N₂) decreased from 0.64 to 6.4 ×10-⁷ Ci.m³ within 155 min when the TRE was operated under the recirculation mode with the flow rate of 200 l-h¹ at the catalyst temperature of 200°C. In addition, the HT-to-HTO fractional conversion was determined at various catalyst temperatures (25–200°C) and flow rates (100–360 lh-¹).     

Room-Temperature Reactor Packed with Hydrophobic Catalysts for the Oxidation of Hydrogen Isotopes Released in a Nuclear Facility

A room-temperature reactor packed with hydrophobic catalysts for the oxidation of hydrogen isotopes released in a nuclear facility will contribute to nuclear safety. The inorganic-based hydrophobic Pt catalyst named H1P has been developed especially for efficient oxidation over a wide concentration range of hydrogen isotopes at room temperature, even in the presence of saturated water vapor. The overall reaction rate constant for hydrogen oxidation with the H1P catalyst in a flow-through system using a tritium tracer was determined as a function of space velocity, hydrogen concentration in carriers, temperature of the catalyst, and water vapor concentration in carriers. The overall reaction rate constant for the H1P catalyst in the range near room temperature was considerably larger than that for the traditionally applied Pt/Al₂O₃ catalyst. Moreover, the decrease in reaction rate for H1P in the presence of saturated water vapor was slight compared with the reaction rate in the absence of water vapor due to the excellent hydrophobic performance of H1P. Oxidation reaction on the catalyst surface is the rate-controlling step in the range near room temperature and the rate-controlling step is shifted to diffusion in a catalyst substratum above 313K due to its fine porosity. The overall reaction rate constant in the range near room temperature was dependent on the space velocity and hydrogen concentration in carriers. The overall reaction rate constants in the range of 1;000=T greater than 3.2 correlated to k _overall[s^?1] = 5.59 × 10⁷ × SV[h^?1] × exp (?67.7 [kJ/mol]/R_gT), where the space velocity range was from 600 to 7,200 h^?1.     

Radiation Blistering of Vanadium Irradiated with 40keV 4He Ions

The vapor pressure of strontium in the temperature range of 494~660°K has been determined by the mass spectrometric Knudsen effusion method. The temperature dependence of the vapor pressure in Pa is given by the equation: log 10.750 ± 0.122 - (8,427±69)/T. From the values of vapor pressure, heats of vaporization of strontium were obtained to be ΔH° _u298= 163.8 ±1.6 kJ/mol by the second law treatment and ΔH°_u298 = 161.9 ±0.5 kJ/mol by the third law treatment.     

New Phase Transitions in Non-Stoichiometric U3O8-x at High Temperatures, (I)

The phase equilibrium of non-stoichiometric U₃O_8-x has been studied by thermogravimetry in the range 765°≦T≦995°C and 10^?4≦Po₂≦1 atm. The results suggest the presence of six phases within U₃O_8-x the phase, separated by second (or higher) order transitions. The relative partial molar free energies, enthalpies and entropies within an each of the six phases, as well as the standard free energies, enthalpies and entropies for the phase changes are calculated and compared with previous works.     

Enrichment of the Uranium Isotopes by Electromigration in a Cation Exchange Membrane

The γ-radiolysis of water subjected to gas bubbling has been studied using a specially desinged gasloop. During the irradiation, N₂ gas was bubbled from the bottom of the irradiation vessel. As the N₂ gas feed rate was raised, the apparent G(H₂) value increased in keeping therewith, from 5 × l0^?3 to 0.26. However in the presence of a sufficient amount of O₂ or H₂O₂, G(H₂) was raised almost to the level of the molecular yield. With reasonable assumptions, it could be concluded that 3～5 × 10^?6 mol/l of H₂O₂ was sufficient to reduce the back reaction of molecular products to less than 10% under the present experimental conditions. It was also found that the G(H₂) value increased with CH₃OH concentration roughly in proportion to log(CH₃OH), and reached 3.1 with 0.1 mol/l CH₃OH.     

Investigation on Space Dependence of C/E Values for Control Rod Worths and Reaction Rate Distributions in ZPPR-10A and -10D Assemblies

In order to investigate the redox equilibrium of uranium ions in molten NaCL-2CsCL, UV-Vis absorption spectrophotometry measurements were performed for U⁴⁺ and U³⁺ in molten NaCL-2CsCL at 923 K under simultaneous electrolytic control of their ratio. Prominent absorption bands at 480 and 570 nm were assigned to U³⁺, and their molar absorptivities were determined to be 1,260±42 and 963±32 mol^?1.l.cm^?1 respectively. From the dependence of the rest potential of the melt on the spectrophotometrically determined ratio of [U⁴⁺]/[U³⁺], the standard redox potential of the couple U⁴⁺/U³⁺ at 923K was determined to be ?1.481±0.004 V vs. Cl₂/Cl^?. Cyclic voltammetry measurements were carried out for the couple U⁴⁺/U³⁺, and the results agreed well with this standard redox potential value. By the results of cyclic voltammetry, a temperature dependence of the standard redox potential was found to be ?2.094+6.639×10^?4 T (T=823-923 K).     

Selective separation and recovery of cesium by ammonium tungstophosphate-alginate microcapsules

A fine crystalline ammonium tungstophosphate (AWP) exchanger with high selectivity towards Cs⁺ was encapsulated in biopolymer matrices (calcium alginate, CaALG). The characterization of the AWP-CaALG microcapsule was examined using SEM/WDS, IR and DTA/TG analyses, and the selective separation and recovery of ¹³⁷Cs were examined by the batch and column methods using simulated (SHLLW) and real high-level liquid waste (HLLW). The free energy (ΔG°) of the ion exchange (NH₄⁺ ↔ Cs⁺) for fine AWP crystals was determined at −13.2 kJ/mol, indicating the high selectivity of AWP towards Cs⁺. Spherical and elastic AWP-CaALG microcapsules (∼700 μm in diameter) were obtained and fine AWP crystals were uniformly immobilized in alginate matrices. Relatively large K_d values of Cs⁺ above 10⁵ cm³/g were obtained in the presence of 10⁻³–1 M Ca(NO₃)₂, resulting in a separation factor of Cs/Rb exceeding 10². The irradiated samples (⁶⁰Co, 17.6 kGy) also exhibited large K_d values exceeding 10⁵ cm³/g in the presence of 2.5 M HNO₃. The K_d values in the presence of 0.1–9 M HNO₃ for 67 elements were determined and the order of K_d value was Cs⁺ ? Rb⁺ > Ag⁺. The breakthrough curve of Cs⁺ had an S-shaped profile, and the breakpoint increased with decreasing flow rate; the breakpoint and breakthrough capacity at a flow rate of 0.35 cm³/min for the column (0.7 g AWP-CaALG) were estimated at 25.2 cm³ and 0.068 mmol/g, respectively. Good breakthrough and elution properties were retained even after thrice-repeated runs. The uptake (%) of Cs⁺ in SHLLW (28 metal components-1.92 M HNO₃, SW-11, JAEA) was estimated at 97%, and the distribution of Cs⁺ and Zr/Ru into the AWP and alginate phases, respectively, were observed by WDS analysis. Further, the selective uptake of ¹³⁷Cs exceeding 99% was confirmed by using real HLLW (FBR “JOYO”, JAEA). AWP-CaALG microcapsules are thus effective for the selective separation and recovery of Cs⁺ from HLLWs.     

Alkali Hydrothermal Synthesis of Zeolites from Coal Fly Ash and Their Uptake Properties of Cesium Ion

Zeolites were synthesized from coal fly ash by hydrothermal treatment with KOH solutions. K-H zeolite (K₂Al₂Si₄O₁₂-nH₂O) was produced under optimum conditions of 160°C, 3 d, 1 M (=mol/dm³) KOH and liquid-solid ratio of 15cm³/g. The uptake behavior of radioactive cesium for the products was investigated by batch and column methods. The uptake equilibrium of Cs+ for the above product was attained within 2h yielding the distribution coefficient of above 10⁴ cm³/g. The uptake of Cs⁺ was followed by a Langmuir adsorption isotherm and the maximum uptake capacity was estimated to be 3.34 mmol/g. The successive removal of Cs⁺ was accomplished through the column packed with granular composites of product-alginate gel polymer.     

The FeSe2(cr) solubility determined by solubility experiments of Se co-existing with Fe

To determine the equilibrium constant for ferroselite (FeSe₂(cr)) dissolution reaction, FeSe₂(cr) solubility experiments were performed at 298 ± 1 K from both the over- and under-saturation directions with Fe–Se precipitates that were aged at 348 K. X-ray diffraction (XRD) analysis detected only FeSe₂(cr) as the Se solid phase in the equilibrated precipitates. The E_h values of the equilibrated suspensions ranged from ?188.6 to ?4.9 mV vs. standard hydrogen electrode (SHE) and the pH values ranged from 6.00 to 8.76. Based on the available thermodynamic data, Se₄^2? and Fe²⁺ are thermodynamically stable within this E_h–pH range. Agreement between the solubility data obtained from the over- and under-saturation directions lends credence to the attainment of equilibrium at 298 ± 1 K. The thermodynamic interpretations using the specific ion interaction theory (SIT) model showed that E_h values and the concentrations of Se and Fe are well represented by the 2FeSe₂(cr) solubility reaction (2FeSe₂(cr) ? 2Fe²⁺ + Se₄^2? + 2e^?) with log₁₀K^○ = ?17.09 ± 0.28. The obtained log₁₀K^○ value falls within the uncertainty limits of the log₁₀K^○ value calculated from the available thermodynamic data.     

Thermodynamic study of UO2 +x by solid state emf technique

A complete set of thermodynamic parameters of UO_{2 +x} — the relative partial molar thermodynamic quantities of oxygen: g(O₂), h(O₂) and s(O₂) as a function of nonstoichiometry x and temperature T — have been determined with sufficient accuracy by the precise emf measurements of the solid state galvanic cell of the type Ni.NiO/Stabilized ZrO₂/UO_{2 + x}, at 0.0030 ⩽ x ⩽ 0.23 between 500 and 1100°C. Nonstoichiometry x was controlled and determined by the coulometric titration of oxide ions at 1000°C by using NiO in the Ni/NiO reference mixture as a source of oxygen.UO_{2 +x} samples of two different preparation procedures give almost identical results and show that g(O₂) versus T plots at various compositions x are not a linear function of temperature, but curve downwards with temperature in the composition and temperature ranges studied. This tendency becomes more pronounced with decreasing nonstoichiometry x and indicates that both h(O₂) and s(O₂) of UO_{2 +x} increase with temperature, their temperature dependence becoming stronger with decreasing nonstoichiometry x.The statistical analysis on about forty emf versus T plots at various compositions x confirms that g(O₂), h(O₂) and s(O₂) of UO_{2 +x} at 0.0030 ⩽ x ⩽ 0.23 and 500 ⩽ T ⩽ 1100°C are accurately expressed by the following equations utilizing the polynomial forms of log x for the temperature independent heat capacity-, entropy- and enthalpy-parameters: c_p(O₂), s₀ and h₀ g(O₂) = h(O₂)−Ts(O₂), s(O₂) =s₀ +c_p(O₂) In T, h(O₂) = h₀ +c_p(O₂)T, where temperature T is in Kelvin, and c_p(O₂), s₀ and h₀ are given by c(O₂) = −43.4642−120.129 log x−60.9395(log x)²− 19.4064(log x)³ (J/mol·K). s₀= −93.807 + 281.272 log x + 119.575(log x)² + 72.651(log x)³ (J/mol·K). h₀ = 373.411 + 277.706 log x + 23.4894(log x)² + 654.207(log x)⁻¹ + 198.212(log x)⁻² (kj/mol).The present results are extensively discussed in comparison with the available literature data on these quantities and also in connection with the point defect model of UO_{2 +x} recently proposed by the present authors.     

Molar Gibbs energy of formation of NaUO3(s)

The sodium pressure over the coexisting phase field, NaUO₃ + Na₂U₂O₇ + Na₂UO₄ was measured using Knudsen effusion mass loss (KEML) and Knudsen cell mass spectrometric (KEMS) methods. The sodium pressure over the coexisting phase field can be represented by: logp_Na(Pa) ± 0.041 = −22701/T (K) + 17.92 (1117–1193 K). The oxygen potential existing over the above phase field was determined by an oxide electrolyte galvanic cell with air and Ni(s) + NiO(s) as reference systems and can be given by: Δμ(O₂) (kJ/mol) ± 0.19 = −716.9 + 0.335T(K) (968–1118 K). The molar Gibbs energy of formation of NaUO₃ calculated from the oxygen and sodium potentials can be represented by: ΔG°_f(NaUO₃), T(K) ± 13.4 kJ/mol = −1487.4 + 0.291 T(K). The second and third law treatment of the present data yielded the standard enthalpy of formation, (Δ_fH°_m, 298.15 K) value of (− 1481.4 ± 13.4) and (−1476.8 ± 13.4) kJ/mol respectively.     

Announcement Meeting calender

The thermal conductivities of (Pu_1?xR_x)O_2?y solid solutions (R = Nd and Y) containing RO_1.5 up to 10 mol% were determined in the temperature range 700–1450 K from thermal diffusivities measured by the laser flash method. The thermal conductivities satisfied the phonon conduction equation K = (A + BT)^?1 within ± 7%. The values of A, corresponding to the lattice defect thermal resistivity, increased linearly with the neodymium or yttrium content, while those of B were nearly constant. The increasing rate of A for (Pu, Nd)O_2?y solid solutions was slightly larger than that for (Pu, Y)O_2?y. These increases were reasonably explained by the lattice defect model in wich Pu⁴⁺, R³⁺, O^2? ions, and oxygen vacancy in the solid solutions were considered as phonon scattering centers. For both solid solutions, the lattice strain effects on the lattice defect thermal resitivities were in preference to the mass effects. In addition, the stoichiometry effects on the additional defect thermal resistivities were about 1.3 times larger than the cation effects.     

Solubility of Uranyl Nitrate Precipitates with N-Alkyl-2-pyrrolidone Derivatives (Alkyl = n-Propyl,n-Butyl,iso-Butyl,and Cyclohexyl)

The solubility of UO₂(NO₃)₂(NRP)₂ (NRP = N-alkyl-2-pyrrolidone) in aqueous solutions with HNO₃ (0–5.0 M) and the corresponding NRP (0–0.50M) has been studied. As a result, the solubility of each speciesof UO₂(NO₃)₂(NRP)₂ generally decreases with increasing concentrations of HNO₃ and the corresponding NRP (C _HNO3 and C _NRP, respectively) in the supernatant. The solubility of UO₂(NO₃)₂(NRP)₂ also depends on the type of NRP; a higher hydrophobicity of NRP generally leads to a lower solubility of UO₂(NO₃)₂(NRP)₂. The logarithms of effective solubility products (K _eff) of UO₂(NO₃)₂(NProP)₂, UO₂(NO₃)₂(NBP)₂, UO₂(NO₃)₂(NiBP)₂, and UO₂(NO₃)₂(NCP)₂ at different C_HNO3 values and 293K were evaluated. For instance, at C_HNO3 = 3:0 M, logK ^NProP _eff = ?1:07 ± 0:03, log K ^NBP _eff = ?2:23 ± 0:02, log K ^NiBP _eff = ?2:59 ± 0:03, and log K ^NCP _eff = ?3:80 ± 0:05. The solubility of UO₂(NO₃)₂(NRP)₂ is determined by the balance among the common-ligand effect, ionic strength, and variation of log K _eff with C _HNO3.