Phase formation in cast stone matrices (CSMs) fabricated through the interaction of comelted basalt with ZrO2 at 1623 K for 5 h on air was studied. Basalt melted under the above conditions contains two spinels (relict and newly formed), clinopyroxene of the composition Mg0.66Ca0.60Fe0.26Ti0.05Al0.66Si1.80O6, and glass as the major phases. When basalt is comelted with ZrO2, taken in a weight ratio of 1 : 1, CSMs containing zircon (ZrSiO4), glass, and baddeleyite (ZrO2) as the major phases are formed. Zirconium is concentrated mainly in two phases, zircon and baddeleyite. The rate of Zr leaching from the synthesized CSMs into H2O after 28 days is 1.0 × 10–9 g/(cm2 day).

This work examines cast stone matrices (CSM) fabricated by comelting of basalt with both uranium-bearing perlite (M150 grade) and U3O8 at a temperature of 1623 K in air for 5 h. As a result of comelting of basalt with uranium-free M150 grade perlite, matrices are obtained containing glass and spinel as the major phases. When basalt is comelted with uranium-bearing perlite (M150 grade) CSMs are formed, the major phases of which are two Cr-spinels of different compositions, uranium-bearing glass, and dendritic aluminosilicate crystals. In the case of fusion of basalt and U3O8 taken in the initial weight ratio of 1 : 1, CSM is generated as the major phases containing UO3, CaU3O10, (Al,Cr,Fe)2U2O9, plagioclase, and uranium-bearing glass. The leaching rate of uranium from a basalt melt with uranium-bearing perlite (M150 grade, 7.2 wt

The release of 137Cs into an Ar flow during the reaction of 137CsI and 137CsOH–137Cs2CO3 with molten lead at a temperature of 852 K was studied. It was determined that during the heating of Pb0 with 137CsI, 137CsOH–137Cs2CO3, and 137CsI–137CsOH–137Cs2CO3 from 2 to 8

The distribution of uranium between different phases of cast stone matrices fabricated by fusion of basalt and uranium-bearing SiO2-based collectors was investigated. It was found that matrices created by fusion of basalt with SiO2 consist of glass, quartz, and spinel as the main phases. A study of the physicochemical properties of collectors based on 30 wt % UO2(NO3)2-bearing SiO2 showed that, after thermal treatment at a temperature of 973 K, they contain uranium only in the form of UO3. The uranium leaching in H2O from SiO2 after its thermal treatment, as well as from a basaltic melt with SiO2, was estimated.

The process of the gas phase treatment to remove CsOH and Cs2MoO4 radioactive aerosols labeled with cesium-137 (hereinafter, 137CsOH and 137Cs2MoO4) was studied using a setup containing elements of a submerged bed scrubber and a spiral filtering element. Water, basalt wool with a fiber diameter of 2.0 μm, perlite, and a mixture of perlite with Ca(OH)2 were used as the submerged bed. With this setup, it is possible to remove more than 99% of 137CsOH and 137Cs2MoO4 radioactive aerosols removed from the gas flow.

The IR spectra of the gas phase formed during the interaction of gaseous CH 3 I with granular sorbents based on SiO 2 and γ-Al 2 O 3 containing various Ag and Ni compounds were studied. It was found that the main gaseous products formed during the interaction of CH 3 I with the studied sorbents based on SiO 2 are CH 3 NO 3 , CH 3 CH 2 NO 3 , CH 3 OCH 3 , CO 2 , and I 2 , and with those based on γ-Al 2 O 3 – CH 3 NO 3 , CH 3 CH 2 NO 3 , CH 3 OCH 3 , CH 3 OH, CO 2 , and I 2 . It is possible that nitromethane CH 3 NO 2 is also present in the reaction products.

The immobilization of uranium in the Al 2 O 3 matrix was studied. For the modification of Al 2 O 3 precursors containing 10 wt % UO 2 (NO 3 ) 2 three methods were applied: 1) heating the precursor in air for 5 h at temperatures of 573, 973, and 1273 K, 2) treatment of the precursor with a 0.5 M solution of hydrazine hydrate (HH) for 2 h, drying to dry air moisture content at 383 K, followed by heating in air for 5 h at temperatures of 573, 973, and 1273 K, and 3) treatment of the precursor with a 2.0 M ammonia solution, followed by drying and heating, as in method (2). X-ray diffraction analysis of the synthesized composites revealed UO 3 hydrates of various compositions after calcination of the materials to T ~600 K and U 3 O 8 after calcination at T > 950 K. After 24 h of contact of the composites with H 2 O at 298 K, the leaching of uranium from the studied samples was ~(10 –2 –10 –3 ) g U/(g day) for the samples calcined at 383 and 573 K and ~(10 –4 –10 –5 ) g U/(g day) for those calcined at 973 and 1273 K.

Catalytic decomposition of N2O in an air flow at at temperatures of ~420 to ~755 K in the presence of γ-Al2O3-based catalysts was studied. It was found that the degree of N2O decomposition in the presence of catalysts containing Mg, Ni, Co, and Fe does not exceed ~25% at a composite temperature of ~735 K and contact duration of the gas flow with the composite of 5–6 s. It was shown that the Al2O3–2RuO2–400 composite enables a nearly full decomposition of N2O in an air flow at temperatures of 738–753 K and contact durations of 7–15 s.

IR spectra of the gas phase formed during the interaction between gaseous CH3I and SiO2-based granular sorbents containing various silver compounds are studied. It is established that the main gaseous products formed by the interaction between CH3I and Ag-containing sorbents based on SiO2 are CH3CH2NO3, CO2, and I2.

Granulated inorganic sorbents based on KSKG silica gel and aluminum oxide modified with Fe(III) compounds were developed for water purification from As(V). Physicochemical properties of synthesized sorbents were studied. It was discovered that the dynamic exchange capacity for As(V) varied in the following series: Al2O3–7Fe–Amk-290 < SiO2–7Fe–Az < SiO2–7Fe–Ox < SiO2–7Fe–Amk-290 < Si2–7Fe–Amk-600.

Sorption of radionuclides ( 90 Sr, 90 Y, 137 Cs, 152 Eu) and nonferrous metals (Cu, Ni, Zn, Pb) from aqueous solutions onto granulated sorbents based on coarsely porous silica gel of KSKG and MSKG grades and on BAU-A activated carbon was studied. The granulated sorbents based on coarsely porous silica gel of KSKG and MSKG grades, modified with Cu, Zn, and Ni ferrocyanides, efficiently take up 90 Sr and 90 Y from distilled water. In tap water, the sorption efficiency for all the sorbents based on KSKG and MSKG does not exceed 70%. The surface of BAU-A was modified by keeping it in a nitrating atmosphere [NO x -air or HNO 3 (vapor)-air] at 90–110°C for 4 h, and also by impregnating it with 10 wt % triethanolamine (TEA), triethylenediamine (TEDA), or urea (CH 4 N 2 O). The sorbents based on BAU-A activated carbon efficiently take up 90 Y (analog of trivalent actinides and lanthanides) and nonferrous metal ions from various aqueous solutions. Modification of BAU-A decreases its sorption capacity for Cu 2+ , Ni 2+ , and Zn 2+ but increases its sorption capacity for Pb 2+ .

Findings from a study of the N2O absorption from an air flow in various aqueous and organic solutions at 293–298 K were reported. The maximum N2O absorption reached under the experimental conditions for water (~22–24%) and a saturated solution of K2Cr2O7 in concentrated H2SO4 with and without Al2O3 (~34 and ~30%, respectively) was determined. In concentrated HNO3 and NH4OH solutions, as well as in 1.0 mol/L NaOH and N2H4 ⋅ nH2O solutions, the degree of the N2O absorption varied within a range from ~7.5 to ~11.5%. A similar value of absorption was also found in 0.5 mol/L (NH2)2CO (~11%). In other solutions, the degree of the N2O absorption was not more than ~4.0%. In the studied organic solutions, the degree of the N2O absorption was found to be less than ~12%.

The design of a new fireproof combined filter for purifying a radioactive steam-gas mixture by removing volatile compounds of radioactive iodine during normal operation of NPP as well as during accidental depressurization of fuel rods is described. The filter consists of identical cylindrical sections, each of which possesses a top lid for anchoring spiral filtering elements with variable surface area and a bottom lid with a grid for anchoring sorbents. The first and closing sections along the course of the purified gas flow are filled with sorbent consisting of the inorganic material SiO2–Cu0 or KSKG brand silica gel or a mixture of the two. A granulated sorbent based on SKT-3I brand activated charcoal or Fizkhimin inorganic granulated sorbent based on silica gel is used as a filler in each of the intermediate sections to catch volatile forms of radioactive iodine. The size of the pores in the spiral filtering elements with variable surface area decreases in a direction from the first to the closing section along the course of the purified gas flow; there are at least three sections equipped with sorbent for purifying gases by removing radioactive iodine-containing impurities.

The possibility of removing dyes from aqueous solutions containing 137 Cs, 90 Sr, 90 Y, and U(VI) using layered double oxides (LDOs) and hydroxides (LDHs) of Mg and Al was examined. The use of LDO-Mg-Al allows rapid and efficient pretreatment of radioactive solutions containing Cs and Sr radionuclides to remove dyes for the subsequent recovery of Cs and Sr with other selective sorbents. The use of LDO-Mg-Al, LDH-Mg-Al-OH, and LDH-Mg-Al-CD (CD is β-cyclodextrin) allows simultaneous removal from aqueous solutions of UO 2 (NO 3 ) 2 (initial concentration <10 −2 M), 90 Y (an analog of trivalent f elements), and dye (degree of removal >90%).

Dinitrogen oxide N2O (nitrogen hemioxide) is one of the harmful components of the off-gases during the reprocessing of spent nitride fuel. It enters the gas phase during the dissolution of nitride fuel in nitric acid and denitration of high-activity raffinate or the bottom solution from the evaporation of intermediate-level wastes. The preferred method of neutralizing it is high-temperature catalytic decomposition. Compositions based on γ-aluminum oxide coated with catalysts were found previously. One of the compositions was checked on a semi-industrial setup. The efficiency of N2O decomposition was studied as a function of temperature. It was established that almost complete decomposition occurs at 465–480°C. The specific rate of N2O decomposition at 425–480°C was found as a function of the initial concentration. It is shown that for constant initial concentration of N2O the specific decomposition rate is almost the same in the investigated temperature interval.