Sorption of microamounts of 137Cs from solutions of various compositions onto semicrystalline alkali metal silicotitanates (TiSi) was studied. The pore structure analysis showed that the TiSi samples formed under the conditions of the experiments had bimodal nanoporosity characterized by the presence of ultramicropores (r ≈0.4–1.0 nm) and transport mesopores (r ≈2.5–30 nm). Potentiometric titration showed that TiSi contained acidic protonogenic groups with pK a ≈1.5–2.5, suggesting the possibility of ion-exchange sorption of alkali metal cations from acid solutions. A study of the 137Cs distribution coefficient on TiSi as a function of the concentrations of sodium, potassium, and ammonium nitrates showed that the cations can be ranked in the following order with respect to the effect on the cesium sorption: Na+ < K+ < NH 4 + . As demonstrated by experiments on the 137Cs removal from simulated bottom residue of nuclear power plants and on treatment of liquid radioactive waste from the Shelter Object of the Chernobyl NPP, semicrystalline alkali metal silicotitanates exhibit high sorption ability and selectivity with respect to 137Cs and can be used for removing cesium from multicomponent salt solutions.

The characteristics of various sorbents based on tetraoctyldiglycolamide (TODGA) in sorption of REE(III), Th(IV), and U(VI) ions from nitric acid solutions were studied. The static capacity of the sorbents increases as the TODGA content of the sorbent and HNO3 concentration in the initial solution are increased. Europium can be desorbed with dilute HNO3 (0.01 M) and complexone (DTPA) solutions. The sorption characteristics of the sorbents in repeated sorption–desorption cycles remain stable. The sorbents prepared by joint copolymerization (solid extactants, SEs) exhibit better sorption and kinetic characteristics compared to the sorbents prepared by impregnation of the ready polymeric matrix.

Equilibrium and kinetic characteristics of template mesoporous silicas containing phosphonic acid residues in sorption of various actinide ions were studied. The sorption equilibrium involving these sorbents is attained within 20 min after introducing the sorbent into the solution. The calculated values of the internal diffusion coefficient \((\bar D)\) and half-exchange time (τ0.5) in sorption of uranium were ∼3.5 × 10−16 m2 s−1 and ∼390 s, respectively. Mesoporous phosphorus-containing silicas efficiently sorb from acid solutions uranyl ions, Th(IV), and Pu(IV). In sorption of uranium from sulfuric acid solutions, the capacity of the sorbents is 125–132 mg g−1, and in sorption from nitric acid solutions (0.5–3.0 M HNO3), 276–299 mg g−1. In sorption of Th(IV) from nitric acid solutions, the capacity of the sorbents is 60–66 mg g−1. In sorption of microamounts of 239Pu(IV), the distribution coefficient reaches 4500 cm3 g−1. Phosphorus-containing silicas in nitric acid solutions do not noticeably sorb 241Am, which allows using them for efficient separation of the Pu/Am pair with the separation factor of no less than 2 × 103.

We propose to test for short baseline neutrino oscillations, implied by the recent reevaluation of the reactor antineutrino flux and by anomalous results from the gallium solar neutrino detectors. The test will consist of producing a 75 kCi 144Ce - 144Pr antineutrino source to be deployed in the Kamioka Liquid Scintillator Anti-Neutrino Detector (KamLAND). KamLAND's 13m diameter target volume provides a suitable environment to measure energy and position dependence of the detected neutrino flux. A characteristic oscillation pattern would be visible for a baseline of about 10 m or less, providing a very clean signal of neutrino disappearance into a yet-unknown, "sterile" state. Such a measurement will be free of any reactor-related uncertainties. After 1.5 years of data taking the Reactor Antineutrino Anomaly parameter space will be tested at > 95% C.L.

The ability of natural and modified montmorillonite clays from Belgorod oblast to sorb Cs, Sr, U, and Pu radionuclides was studied. The clays were modified by treatment with metal (Li+, Na+, K+, Mg2+, Ca2+, Fe2+, Zn2+) chloride solutions or aqueous HCl. The natural and modified clays studied show high performance in sorption treatment of solutions to remove Cs radionuclides. The natural clay and the Na and Mg forms of clays show the best sorption characteristics with respect to Cs. The distribution coefficient K d of 137Cs in sorption on the above samples from a 0.1 M NaNO3 solution is (1.1–1.4) × 104 cm3 g−1, which is 4–5 times higher compared to natural clinoptilolite. The Sr, U, and Pu radionuclides are sorbed on the examined clay samples to a considerably lesser extent. The K d values in sorption of these radionuclides from tap water are lower by 2–3 orders of magnitude than in sorption of Cs. Addition of clay materials in the course of cementation of liquid radioactive wastes, including NPP bottom residues, allows the rate of radiocesium leaching from the hardened cement compounds to be decreased by a factor of 5–16. The most efficient sorption additive in cementation of NPP bottom residues is natural montmorillonite clay.

Sorption of transplutonium (TPE) and rare-earth (REE) elements on Purolite®S-957 ion exchanger containing phosphonic acid and sulfo groups was studied. Rare-earth elements are efficiently sorbed from weakly acidic solutions (≤0.1 M HNO 3 ). An increase in the solution acidity and introduction of sodium ions into the sorption medium lead to a decrease in the sorption. With S-957 resin, REE and TPE were separated for the first time on a phosphorus-containing sorbent by displacement chromatography in the presence of DTPA (diethylenetriaminepentaacetic acid).

Sorption of Pu4+, UO 2 2+ , NpO 2 + , Am3+, and Eu3+ ions on S-957 cation exchanger from 2–7 M HNO3 solutions was studied. The following selectivity series was obtained: Pu4+ > UO 2 2+ > NpO 2 + > Am3+ ≈ Eu3+. The static and dynamic capacities of the sorbent for Pu were determined, and the eluent composition for the efficient desorption was chosen. The possibility of separating Pu(IV)-Am(III) and Pu(IV)-Np(V) pairs on the sorbent in the column chromatography mode was demonstrated.

Accumulation of Ce(IV) in HNO3 solutions as a result of Ce(III) oxidation with an ozone-oxygen mixture (OOM) was studied. An increase in the ozone concentration in OOM from 30 to 180 mg dm−3 leads to a considerable increase in the rate of Ce(III) oxidation to Ce(IV). With concentrated OOM, the Ce(III) to Ce(IV) oxidation yield of two ions per ozone molecule is attained. An increase in the steady-state concentration of Ce(IV) in the solution leads to considerable acceleration of the dissolution of highly calcined UO2.

The solidification of partially evaporated bottoms of RBMK and VVER with salt concentration 500–650 g/liter by compositional binders consisting of Portland cement and silicic additives – aerosil, microsilica, opoka, silicic acid, liquid glass, and diatomite is examined. The additions were used to obtain matrices that satisfy the requirements of safe storage of cemented radwastes. The partition coefficients of 137Cs in partially evaporated bottoms are determined for all additives studied. The most effective additive for solidification of partially evaporated bottoms of VVER is diatomite. Matrices with diatomite have strength 50–81 kg/cm2, the rate of leaching of 137Cs ~ 10–3–10–4 g/(cm2·day) and the fill with respect to salts reaches 20.9 wt.%. On the solidification of partially evaporated RBMK bottoms the most effective hardening additives are aerosil and microsilica and the most effective sorbing additives are bentonite, opoka, and diatomite. The matrices so obtained have strength 59–93 kg/cm2, 137Cs leach rate ~ 10–3–10–4 g/(cm2·day) and contain to 25.1 wt.% salts.

Plutonium dioxide recovered in the course of reprocessing of SNF from WWER reactors (so-called high-level PuO2) was subjected to dissolution in 0.6–3.0 M HNO3 in the presence of Am(III) ions under ozonation with an ozone-oxygen mixture containing 30–180 mg l−1 O3. Measurements of the rate of the PuO2 dissolution in 3 M HNO3 in the temperature interval from 30 to 80°C showed that, with an increase in the ozone concentration in the ozone-oxygen mixture from 30 to 180 mg l−1, the dissolution rate increases by a factor of 4–5. The acceleration of the PuO2 dissolution is attributed to the formation of Am(V,VI) by homogeneous oxidation of Am(III) ions with ozone dissolved in HNO3. The Am dioxocations formed act as PuO2 oxidants and are continuously regenerated by the oxidation of Am(III) with ozone. This assumption is confirmed by an additional increase in the dissolution rate, observed on introducing Am(III) into the initial electrolyte for the PuO2 dissolution.

The radiolytic behavior of FNS composite ferrocyanide sorbent based on potassium nickel ferrocyanide and silica gel was studied. γ-Irradiation of the sorbent results in formation of hydrogen due to radiolytic decomposition of water in the solid phase. The hydrogen yield (molecules/100 eV) is 0.02 for the dry sorbent and 0.07 for the wet sorbent. The amount of hydrogen formed in the course of storage of the sorbent saturated with 137Cs was calculated. On irradiation of the dry sorbent in the potassium form to a dose of 4 MGy, the 137Cs distribution coefficient K d decreases by a factor of 2.5. However, K d of 137Cs on irradiated sorbents remains sufficiently high (>104), i.e., the FNS ferrocyanide sorbent shows high functional resistance to radiation. γ-Irradiation of dry and wet samples of the ferrocyanide sorbent to a dose of 4 MGy does not lead to oxidation of Fe(II) to Fe(III) in [Fe(CN)6] groups. Thus, FNS ferrocyanide sorbent is a radiation-resistant material suitable for recovery of cesium radionuclides from liquid radioactive wastes and the subsequent long-term and safe storage.

The behavior of microconcentrations of radionuclides (with Pm as example) in REE separation by displacement complexing chromatography was studied. The Pm elution curve is bell-shaped but obeys the laws of displacement chromatography. Addition of citric acid salts to the DTPA-based eluent makes the REE separation more efficient.

Sorption of microamounts of cesium on finely dispersed composite ferrocyanide sorbents was studied. The sorbents were prepared by precipitation of nickel potassium ferrocyanide in the presence of various mineral supports (chalk, wollastonite, bentonite, clinoptilolite, diatomite, biosilica). The distribution coefficient ( K d ) of 137 Cs on composite ferrocyanide sorbents is considerably higher than on nickel potassium ferrocyanide without support. The K d values on the composite sorbents increase by a factor of 25–110 when separating the solid phase with a paper filter and by a factor of 4.3–8.2 when using a microfiltration membrane. Considerable increase in K d of 137 Cs on composite sorbents is attributed to the formation of a nickel potassium ferrocyanide phase firmly fixed on the support surface and resistant to peptization. Composite ferrocyanide sorbents were tested for the 137 Cs recovery from a simulated NPP bottom residue in the pH range 8.5–12.0. On the composite sorbents, K d of 137 Cs is 2.5–3.0 times higher than on the nickel ferrocyanide precipitate throughout the examined pH range. The composite sorbent based on biosilica and nickel potassium ferrocyanide was tested for treatment of real liquid radioactive waste with a total salt content of 22.0 g dm −3 to remove 137 Cs. The decontamination factor as high as 5190 was attained owing to simultaneous use of the finely dispersed composite ferrocyanide sorbent and an ultrafiltration ceramic membrane.

Sorption of Th, uranyl, Am, Fe, and Al ions from nitric acid solutions on various phosphorus-containing ion-exchange materials (organic ion-exchange resins, SE-UPO solid extractant) was studied. The highest selectivity to quadruple-charged metal cations is exhibited by S-957 cation exchanger (Purolite) with phosphonic and sulfonic acid groups. The capacity of this resin for Th is essentially independent of the HNO3 concentration in the range 1–7 M and amounts to 80–95 mg ml−1. The uranyl, Am, Fe, and Al ions are sorbed on S-957 resin considerably worse than Th. The internal diffusion coefficient of Th4+ ions in S-957 resin from 3 M HNO3 was determined to be (5.3 ± 0.5) × 10−13 m2 s−1. The IR spectra of S-957 resin in the hydrogen and thorium forms were recorded. S-957 resin shows promise for selective recovery of tetravalent actinides from multicomponent nitric acid-salt solutions.

Oxidative decomposition of EDTA in aqueous solution under the action of ozone was studied. Conditions providing complete decomposition of EDTA and precipitation of radioactive cobalt in the form of hydroxide were found.