Hydrophilic interaction liquid chromatography: An efficient tool for assessing thorium interaction with phosphorylated biomimetic peptides.

In the field of nuclear toxicology, the knowledge of the interaction of actinides (An) with biomolecules is of prime concern in order to elucidate their toxicity mechanism and to further develop selective decorporating agents. In this work, we demonstrated the great potential of hydrophilic interaction liquid chromatography (HILIC) to separate polar thorium (Th) biomimetic peptide complexes, as a key starting point to tackle these challenges. Th4+ was used as plutonium (Pu4+) analogue and pS16 and pS1368 as synthetic di- and tetra-phosphorylated peptides capable of mimicking the interaction sites of these An in osteopontin (OPN), a hyperphosphorylated protein. The objective was to determine the relative affinity of pS16 and pS1368 towards Th4+, and to evaluate the pS1368 selectivity when Th4+ was in competition complexation reaction with UO22+ at physiological pH. To meet these aims, HILIC was simultaneously coupled to electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS), which allowed to identify online the molecular structure of the separated complexes and quantify them, in a single step. Dedicated HILIC conditions were firstly set up to separate the new dimeric Th2(peptide)2 complexes with good separation resolution (peptide = pS16 or pS1368). By adding pS16 and pS1368 in different proportions relatively to Th4+, we found that lower or equal proportions of pS16 with respect to pS1368 were not sufficient to displace pS1368 from Th2pS13682 and pS16 proportion higher than pS1368 led to the formation of a predominant ternary complex Th2(pS16)(pS1368), demonstrating preferential Th4+ binding to the tetra-phosphorylated peptide. Finally, online identification and quantification of the formed complexes when Th4+ and UO22+ were mixed in equimolar ratio relatively to pS1368 showed that in spite of pS1368 has been specifically designed to coordinate UO22+, pS1368 is also Th4+-selective and exhibits stronger affinity for this latter than for UO22+. Hence, the results gathered through this approach highlight the impact of Th4+ coordination chemistry on its interaction with pS1368 and more widely to its affinity for biomolecules.

Plutonium Speciation and Oxidation State Distributions in the Presence of Citrate.

We explored the speciation and kinetics of the Pu(VI)-citrate and Pu(III)-citrate systems (pHm = 2.5-11.0, I = 0.1 M NaCl, T = 23 °C, O2(g) < 2 ppm) using ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometry, solvent extraction, and PHREEQC modeling. Formation constants were determined for PuO2(HcitH)(aq) (log K°1,1 = 1.09 ± 0.05) and PuO2(HcitH)(citH)3- (log K°1,2 = -0.20 ± 0.07), and evidence for (PuO2)m(citH-k)n(OH)x2m(3+k)n-x was identified under alkaline conditions. Pu(VI) species were found to be less stable in the presence of citrate than in the absence of citrate (t ≤ 168 days); the rate of reduction increased with increasing pH. The direct reduction of Pu(VI) to Pu(IV) was required to fit experimental data in the presence of citrate but did not improve the fit for Pu in the absence of citrate. We also observed increased Pu(III) stability in the presence of citrate (t ≤ 293 days), with higher concentrations of Pu(III) favored at lower pH. Finally, we provide evidence of a radiolysis-driven mechanism for the citrate-mediated reduction of plutonium that involves electron transfer from the oxidative breakdown of citrate. Our work highlights the need to investigate the redox effect of organic ligands on plutonium oxidation states under repository-relevant conditions.

Going deeper into plutonium sorption affected by redox.

Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet-visible (UV-Vis) spectroscopy and liquid-liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions.

A multi-collector ICP-MS method for quantification of plutonium, uranium, and americium in hair and nails of occupationally or medically exposed individuals.

The 239Pu, 238U, and 241Am concentrations and 239Pu/240Pu, 235U/238U, and 236U/238U atom ratios were measured in the hair and nail samples using a new method utilized TEVA, UTEVA, and DGA extraction chromatography and multi-collector ICP-MS. Samples were collected from individuals who donated their bodies to the United States Transuranium and Uranium Registries. The concentration of 239Pu ranged from 0.22 to 15.8 ng/kg. The 240Pu/239Pu isotopic ratios ranged from 0.026 to 0.127 which is consistent with weapons-grade plutonium. Concentration of uranium fell between 1.84 µg/kg and 29.5 µg/kg and 235U/238U ratios ranged from 4.8 × 10-3 to 7.6 × 10-3. Elevated 236U/238U atom ratios were measured in two cases and ranged from 5.0 × 10-6 - 2.4 × 10-5 indicating exposure to spent or reprocessed uranium material. The concentration of 241Am was measured in four hair samples and ranged from 0.02 to 0.21 ng/kg.

Predominance of the alkaline earth(II) triscarbonatoactinyl(VI) complexes in different geochemical contexts: Review of existing data and estimation of potentially unidentified species.

From the available thermodynamic data in the literature, a review of the impact of the formation of complexes between triscarbonatoactinyl(VI) and alkaline earth(II) (Ae) is estimated under varying conditions. First, after analyzing the literature data and using the ascertained thermodynamic data available from the commissioned reviews from the Nuclear Energy Agency (Organization for the Economic Cooperation and Development) Thermochemical DataBank Project on actinides (An) U, Np, and Pu, and from recently determined AenUO2(CO3)3(4-2n)- thermodynamic functions, the formation of AenAnO2(CO3)3(4-2n)- complexes for Pu(VI) and Np(VI) are estimated using linear free energy relationships (LFERs). The data are in good agreement with the sole determination of AePuO2(CO3)32- from Jo et al. (Dalton Trans. 49, 11605), which gives a relative confidence in the LFERs, and allows the application to actual situations. From existing uranium data, first, the impact of the origin of the data on the calculated predominance is addressed under 0.1 M NaCl and atmospheric CO2(g); second, the influence of ionic strength and salinity on predominance is estimated; and finally, the influence of temperature up to 50 °C on the solubility of uraninite in a deep geological radioactive waste storage or disposal site is calculated. For neptunium and plutonium, the impact of the potential log10ß°(AenAnO2(CO3)3(4-2n)-) on Pourbaix diagrams of Pu and Np in Mg-Ca-CO3 media are estimated from Jo et al. (Dalton Trans. 49, 11605) and LFERs. Finally, the application to the speciation of Pu and Np in seawater is proposed.

Interaction Between the Transferrin Protein and Plutonium (and Thorium), What's New?

Transferrin (Tf) is a glycoprotein that transports iron from the serum to the various organs. Several studies have highlighted that Tf can interact with metals other than Fe(III), including actinides that are chemical and radiological toxics. We propose here to report on the behavior of Th(IV) and Pu(IV) in comparison with Fe(III) upon Tf complexation. We considered UV-Vis and IR data of the M2 Tf complex (M=Fe, Th, Pu) and combined experimental EXAFS data with MD models. EXAFS data of the first M-O coordination sphere are consistent with the MD model considering 1 synergistic carbonate. Further EXAFS data analysis strongly suggests that contamination by Th/Pu colloids seems to occur upon Tf complexation, but it seems limited. SAXS data have also been recorded for all complexes and also after the addition of Deferoxamine-B (DFOB) in the medium. The Rg values are very close for apoTf, ThTf and PuTf, but slightly larger than for holoTf. Data suggest that the structure of the protein is more ellipsoidal than spherical, with a flattened oblate form. From this data, the following order of conformation size might be considered:holoTf

Investigation of the Plutonium(IV) Interactions with Two Variants of the EF-Hand Ca-Binding Site I of Calmodulin.

Due to its presence in the nuclear industry and its strong radiotoxicity, plutonium is an actinide of major interest in the event of internal contamination. To improve the understanding of its mechanisms of transport and accumulation in the body, the complexation of Pu(IV) to the most common protein calcium-binding motif found in cells, the EF-hand motif of calmodulin, was investigated. Visible and X-ray absorption spectroscopies (XAS) in solution made it possible to investigate the speciation of plutonium at physiological pH (pH 7.4) and pH 6 in two variants of the calmodulin Ca-binding site I and using Pu(IV) in different media: carbonate, chloride, or nitrate solutions. Three different species of Pu were identified in the samples, with formation of 1:1 Pu(IV):calmodulin peptide complexes, Pu(IV) reduction, and formation of peptide-mediated Pu(IV) hexanuclear cluster.

The Influence of Iron and Ligand Type on Plutonium Uptake in Two Strains of Hydroponically Grown Corn ( Zea Mays ).

ABSTRACT: This work investigates the uptake and root-shoot transport of plutonium (Pu) and iron (Fe) in corn ( Zea mays ) to gain insight into the Pu uptake pathway. Plutonium has no known biological function in plants yet may feasibly enter plants through the uptake pathway used by Fe (an essential nutrient), as these two elements have similar chemical properties. A series of experiments was conducted in which two hydroponically grown corn strains (one normal and one deficient in the transporter protein for Fe) were exposed to varying concentrations of complexed Pu and Fe. Results suggest that while Fe did inhibit Pu uptake to a certain extent, Pu was able to use alternative uptake pathways. In a 10 ppb Pu:1 ppb Fe hydroponic solution, all shoots had detectable shoot Pu concentrations compared to only 22% of plants when the Fe concentration was raised to 10 ppb. While root Pu accumulation was reduced for the corn strain deficient in the Fe transporter protein at lower Pu media concentrations, there were no differences at higher Pu concentrations, signifying the existence of substitute transport routes. A comparison of citrate and deferoxamine B (DFOB) ligand influence found that Pu complexed with DFOB remained in the roots of the plant, while movement of Pu into the shoots of the plant was more prevalent with the Pu-citrate complex. This study advances understanding of the behavior and mobility of Pu in the terrestrial environment and specifically the interactions between Pu and an essential nutrient in a common crop species.

Use of an Acellular Assay to Study Interactions between Actinides and Biological or Synthetic Ligands.

Speciation of actinides, and more particularly bioligand-binding ability, influences in vivo behavior. Understanding these interactions is essential for estimation of radiological dose and improvement of decorporation strategies for accidentally contaminated victims. Because the handling of actinides imposes overwhelming difficulties, in vitro assays carried out in physiological conditions are lacking and data regarding such interactions are scarce. In this study, we used a bi-compartmental and dynamic assay, providing physiological conditions (presence of inorganic ions, pH, temperature) to explore interactions between the actinides plutonium (Pu) and americium (Am) and endogenous (proteins transferrin and ferritin) or exogenous ligands (the chelating agent diethylenetriaminpentaacetic acid, DTPA). In this assay, an agarose gel represents the retention compartment of actinides and a dynamic fluid phase, the transfer compartment. The proportion of actinides transferred from static to dynamic phase reflects interactions between Pu/Am and various ligands. The results show differences in the formation of actinide-protein or actinide-DTPA complexes in physiologically relevant media depending on which ligand is present and where. We observed differential behavior for Pu and Am similar to in vivo studies. Thus, our assay may be used to determine the ability of various actinides to interact with specific proteins or with drug candidates for decorporation in complex physiologically relevant environments.

3D printed field-deployable microfluidic systems for the separation and assay of Pu in nuclear forensics.

A compact field-deployable microfluidic system has been developed to improve timelines for the rapid analysis of debris in post-detonation nuclear forensics. We used a high-resolution 3D printer to miniaturize typical laboratory-based procedures into a fieldable platform. Microfluidic half-modules were produced for the purification of Pu from excess U, along with a portable alpha chamber for the following isotopic analysis of the Pu stream. A porous PTFE membrane is soaked with a hydrophobic tributyl phosphate (TBP) solution and is placed between two half-modules; separation is performed as a liquid-liquid extraction in an extraction channel across this membrane, where the forward and back-extractions occur within one complete module. Following separation, a 100 µL sampling of the Pu-bearing stream is injected into a small-footprint 3D printed alpha chamber for isotopic assay via alpha spectrometry as part of an online process. In this first demonstration of microfluidic separation coupled with online alpha spectrometry, high extraction yields have been obtained for Pu (98.9 ± 4.0)% and U (97.5 ± 2.5)%. The process uses less than 800 µL of solution with separation chemistry complete within 45 minutes and subsequent alpha spectrometry initiating 25 minutes after separation.

Chelating Polymers for Targeted Decontamination of Actinides: Application of PEI-MP to Hydroxyapatite-Th(IV).

In case of an incident in the nuclear industry or an act of war or terrorism, the dissemination of plutonium could contaminate the environment and, hence, humans. Human contamination mainly occurs via inhalation and/or wounding (and, less likely, ingestion). In such cases, plutonium, if soluble, reaches circulation, whereas the poorly soluble fraction (such as small colloids) is trapped in alveolar macrophages or remains at the site of wounding. Once in the blood, the plutonium is delivered to the liver and/or to the bone, particularly into its mineral part, mostly composed of hydroxyapatite. Countermeasures against plutonium exist and consist of intravenous injections or inhalation of diethylenetetraminepentaacetate salts. Their effectiveness is, however, mainly confined to the circulating soluble forms of plutonium. Furthermore, the short bioavailability of diethylenetetraminepentaacetate results in its rapid elimination. To overcome these limitations and to provide a complementary approach to this common therapy, we developed polymeric analogs to indirectly target the problematic retention sites. We present herein a first study regarding the decontamination abilities of polyethyleneimine methylcarboxylate (structural diethylenetetraminepentaacetate polymer analog) and polyethyleneimine methylphosphonate (phosphonate polymeric analog) directed against Th(IV), used here as a Pu(IV) surrogate, which was incorporated into hydroxyapatite used as a bone model. Our results suggest that polyethylenimine methylphosphonate could be a good candidate for powerful bone decontamination action.

In situ beam reduction of Pu(IV) and Bk(IV) as a route to trivalent transuranic coordination complexes with hydroxypyridinone chelators.

The solution-state interactions of plutonium and berkelium with the octadentate chelator 3,4,3-LI(1,2-HOPO) (343-HOPO) were investigated and characterized by X-ray absorption spectroscopy, which revealed in situ reductive decomposition of the tetravalent species of both actinide metals to yield Pu(III) and Bk(III) coordination complexes. X-ray absorption near-edge structure (XANES) measurements were the first indication of in situ synchrotron redox chemistry as the Pu threshold and white-line position energies for Pu-343-HOPO were in good agreement with known diagnostic Pu(III) species, whereas Bk-343-HOPO results were found to mirror the XANES behavior of Bk(III)-DTPA. Extended X-ray absorption fine structure results revealed An-OHOPO bond distances of 2.498 (5) and 2.415 (2) Šfor Pu and Bk, respectively, which match well with bond distances obtained for trivalent actinides and 343-HOPO via density functional theory calculations. Pu(III)- and Bk(III)-343-HOPO data also provide initial insight into actinide periodicity as they can be compared with previous results with Am(III)-, Cm(III)-, Cf(III)-, and Es(III)-343-HOPO, which indicate there is likely an increase in 5f covalency and heterogeneity across the actinide series.

In vitro evidence of the influence of complexation of Pu and Am on uptake by human lung epithelial cells Calu-3.

Understanding the mechanisms involved in retention and clearance of actinides from the lungs after accidental intake is essential for the evaluation of the associated radiological risks. Although the absorption of radioelements has been shown in vivo to depend on their nature and physico-chemical properties, their mechanisms of translocation remain unknown. In this study, we have evaluated in vitro the binding and uptake by bronchial epithelial cells Calu-3 of 2 transuranic actinides, plutonium (Pu) and americium (Am), as the first steps of translocation across the pulmonary barrier. For this purpose, Calu-3 cells grown to confluence in 24-well plates were exposed to the radioelements for 24 h under various culture conditions. Two compartments were identified for the association of actinides to cells, corresponding to the membrane bound and internalized fractions. Binding of Pu was slightly higher than of Am, and depended on its initial chemical form (nitrate, citrate, colloids). Uptake of Pu and Am nitrate was higher in serum-free conditions than in supplemented medium, with an active mechanism involved in Pu internalization. Overall, our results suggest that complexation of actinides to bioligands may have an influence on their uptake by pulmonary epithelial cells, and therefore possibly on their subsequent absorption into blood.

How Does Iron Storage Protein Ferritin Interact with Plutonium (and Thorium)?

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The ferritin-thorium load curve suggests that ThIV saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (spectrophotometry, infrared spectroscopy, and X-ray absorption spectroscopy) were combined with molecular dynamics to provide a structural model of the interaction of ThIV and PuIV with ferritin. Comparison of spectroscopic data together with MD calculations suggests that ThIV and PuIV are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of ThIV and PuIV interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology.

DTPA-Coated Liposomes as a New Delivery Vehicle for Plutonium Decorporation.

Administration of diethylenetriaminepentaacetic acid (DTPA) is the treatment approach used to promote the decorporation of internalized plutonium. Here we evaluated the efficacy of PEGylated liposomes coated with DTPA, primarily designed to prevent enhanced plutonium accumulation in bones, compared to marketed nonliposomal DTPA and liposomes encapsulating DTPA. The comparative effects were examined in terms of reduction of activity in tissues of plutonium-injected rats. The prompt treatment with DTPA-coated liposomes elicited an even greater efficacy than that with liposome-encapsulated DTPA in limiting skeletal plutonium. This advantage, undoubtedly due to the anchorage of DTPA to the outer layer of liposomes, is discussed, as well as the reason for the loss of this superiority at delayed times after contamination. Plutonium complexed with DTPA-coated liposomes in extracellular compartments was partly diverted into the liver and the spleen. These complexes and those directly formed inside hepatic and splenic cells appeared to be degraded, then released from cells at extremely slow rates. This transitory accumulation of activity, which could not be counteracted by combining both liposomal forms, entailed an underestimation of the efficacy of DTPA-coated liposomes on soft tissue plutonium until total elimination probably more than one month after treatment. DTPA-coated liposomes may provide the best delivery vehicle of DTPA for preventing plutonium deposition in tissues, especially in bone where nuclides become nearly impossible to remove once fixed. Additional development efforts are needed to limit the diversion or to accelerate cell release of plutonium bound to DTPA-coated liposomes, using a labile bond for DTPA attachment.

Prediction of Binding Stability of Pu(IV) and PuO2(VI) by Nitrogen Tridentate Ligands in Aqueous Solution.

Plutonium has potential applications in energy production in well-controlled nuclear reactors. Since nuclear power plants have great merit as environmentally friendly energy sources with a recyclable system, a recycling system for extracting Pu from spent fuels using suitable extractants has been proposed. Pu leakage is a potential environmental hazard, hence the need for chemical sensor development. Both extractants and chemical sensors involve metal-ligand interactions and to develop efficient extractants and chemical sensors, structural information about Pu ligands must be obtained by quantum calculations. Herein, six representative nitrogen tridentate ligands were introduced, and their binding stabilities were evaluated. The tridentate L6, which contains tri-pyridine chelate with benzene connectors, showed the highest binding energies for Pu(IV) and PuO2(VI) in water. Analysis based on the quantum theory of atoms in molecular analysis, including natural population analysis and electron density studies, provided insight into the bonding characteristics for each structure. We propose that differences in ionic bonding characteristics account for the Pu-ligand stability differences. These results form a basis for designing novel extractants and organic Pu sensors.

First-Principles Study of Nitrogen Adsorption and Dissociation on PuH2 (111) Surface.

Plutonium mononitride is one of the main fuels for Generation IV reactors and can be prepared from nitrogenation of plutonium hydride. We investigated the adsorption and dissociation of nitrogen on PuH2 (111) surface to elaborate the initial stage of nitrogenation. The adsorption energies varied greatly with respect to the adsorption sites and orientations of the adsorbed molecule. The nitrogen exhibited preferential adsorption above the ccp site, where the molecular nitrogen was nearly parallel to the PuH2 surface and pointed to the nearest Pu atom. The orbital hybridization and the electrostatic attraction between the Pu and N weakened the N-N bond in the adsorbed molecule. The mechanism of the dissociation process was investigated within transition state theory, and the analysis of the activation barrier indicated that dissociation of nitrogen is not the rate-determining step of nitrogenation. These findings can contribute to a better understanding of the nuclear fuel cycle.

Molecular dynamics simulations of plutonium binding and its decorporation from the binding-cleft of human serum transferrin.

The possibility of plutonium (Pu) intake by radiation workers can not be ruled out. Transportation of Pu(IV) to various organs/cells is mainly carried through iron-carrying protein, serum transferrin (sTf), by receptor-mediated endocytosis. Understanding the Pu-sTf interaction is a primary step toward future design of its decorporating agents. We report MD simulations of Pu(IV) binding with sTf and look out for its decorporation at extracellular pH using suitable ligands. MD simulations were carried out in polarizable water environment at different protonation states of the protein. Results unravel the binding motif of Pu(IV): (1) sTf binds the ion in closed conformation at extracellular serum pH with carbonate as synergistic anions, (2) change in protonation state of dilysine (K206 and K296)-trigger and that of the carbonate ion at acidic endosomal pH is found to cause conformational changes of protein, conducive for the heavy ion to be released, although; (3) strong electrostatic interaction between D63 in the binding-cleft and Pu(IV) is found not to ever set free the ion. In an endeavour to decorporate Pu(IV), fragmented molecular form of hydroxypyridinone (HOPO) and catechol (CAM)-based ligands are docked at the binding site (BS) of the protein and metadynamics simulations are conducted. Pu(IV) binding at BS is found to be so strong that it was not detached from BS with the docked HOPO. However, for the identical set of simulation parameters, CAM is found to facilitate dislodging the heavy ion from the protein's binding influence. Differential behaviour of the two chelators is further explored. Fragmented molecular form of hydroxy-pyridinone (HOPO) and catecholamide (CAM) ligands were docked at the binding-site (BS) of human serum transferrin (sTf) to explore their feasibility as plausible Pu(IV) decorporating agents by employing metadynamics method. CAM was found to dislodge Pu from the sTf BS, while HOPO could not.

Chelation Modeling: The Use of Ad Hoc Models and Approaches to Overcome a Dose Assessment Challenge.

Chelating agents are administered to treat significant intakes of radioactive elements such as plutonium, americium, and curium. These drugs may be used as a medical countermeasure after radiological accidents and terrorist acts. The administration of a chelating agent, such as Ca-DTPA or Zn-DTPA, affects the actinide's normal biokinetics. It enhances the actinide's rate of excretion, posing a dose assessment challenge. Thus, the standard biokinetic models cannot be directly applied to the chelation-affected bioassay data in order to assess the radiation dose. The present study reviews the scientific literature, from the early 1970s until the present, on the different studies that focused on developing new chelation models and/or modeling of bioassay data affected by chelation treatment. Although scientific progress has been achieved, there is currently no consensus chelation model available, even after almost 50 y of research. This review acknowledges the efforts made by different research groups, highlighting the different methodology used in some of these studies. Finally, this study puts into perspective where we were, where we are, and where we are heading in regards to chelation modeling.

The Influence of Zeolite (Sokyrnytsya Deposit) on the Physical and Chemical Resistance of a Magnesium Potassium Phosphate Compound for the Immobilization of High-Level Waste.

The manuscript presents the results of the development of new material for high-level waste (HLW) management: the magnesium potassium phosphate (MKP) compound. The possibility of using zeolite (Sokyrnytsya deposit) to increase the mechanical, thermal, and hydrolytic resistance of this compound with immobilized HLW was studied. The main component of the used natural zeolite is a mineral of the clinoptilolite-heulandite series, and quartz, microcline, and clay minerals (illite, sepiolite, and smectite) are present as impurities. The compressive strength of the compound, containing at least 4.2 wt % zeolite, is about 25 MPa. Compound containing 28.6 wt % zeolite retains high compressive strength (at least 9.0 MPa), even after heat treatment at 450 °C. The adding of zeolite to the composition of the compound increases its hydrolytic stability, while the leaching rate of the mobile nuclides 137Cs and 90Sr decreases up to one order of values. Differential leaching rate of radionuclides from the compound containing 28.6 wt % zeolite is 2.6 × 10-7 for 137Cs, 2.9 × 10-6 for 90Sr, 1.7 × 10-9 for 239Pu, and 2.9 × 10-9 g/(cm2∙day) for 241Am. Thus, the properties of the resulting compound correspond to the requirements for solidified HLW in Russia.