Liquid Radioactive Waste Disposal Research Articles

Catalytic oxidation behavior of Sr doped cation exchange resins in Li2CO3–Na2CO3–K2CO3 system

Ion exchange resins are widely applied in radioactive liquid waste disposal. However, problems such as the volatilization of radionuclides, acid gas generation, and self-radiolysis by spent cation exchange resins (CERs) demand the development of appropriate treatment methods. Thus, in the present study, the oxidation behaviors were determined for CERs and Sr doped CERs with Li2CO3–Na2CO3–K2CO3 by thermogravimetric analysis. Ternary alkaline molten carbonate with a low melting point was applied for the first time to treat the Sr doped CERs. This method can reduce the energy consumed disposing of CERs and neutralize the tail gases produced by the oxidation of CERs. The oxidation products were analyzed by on-site gas mass spectrometry, infrared spectroscopy, X-ray diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy. After the sulfonic acid group (-SO3H) decomposed at 300 °C, Sr species did not accelerate the oxidation of residues initially. However, they inhibited the removal of sulfur from the oxidizing residue. The carbonate salt melted at 400 °C and the molten salt effectively alleviated the volatilization of Sr and SO2, which were trapped as SrCO3 and sulfate in the molten salt. Moreover, the presence of Sr2+ significantly enhanced the removal of sulfur from residues to 69.27% from 54.77%, and effectively increased the destruction and removal efficiency of CERs from 47.31% to 60.35% at 450 °C. These findings demonstrate that molten carbonate salt could be a suitable medium for improving the catalytic performance of Sr.

Ultramicrobacteria from Nitrate- and Radionuclide-Contaminated Groundwater

The goal of the present work was to investigate the physicochemical and radiochemical conditions and the microbial diversity in groundwater collected near the Lake Karachai (Russia), which was formerly used for the disposal of liquid radioactive waste, to isolate the dominant bacteria, and to determine their taxonomy and the physiological characteristics responsible for their adaptation to this environment. Groundwater samples contained high concentrations of acetate, oxalate, nitrate, and sulfate, as well as radionuclides. High-throughput sequencing and analysis of the clone libraries revealed lower microbial diversity in the most strongly contaminated groundwater and a predominance of bacteria of the genera Polynucleobacter, Pusillimonas, Candidatus Pelagibacter, and of the candidate phylum Parcubacteria; these groups include species with an ultra small cell size. Archaeal sequences in the libraries belonged to ammonium oxidizers of the phylum Thaumarchaeota and methanogens of the phylum Euryarchaeota. Pure cultures of obligate and facultative ultramicrobacteria belonging to the genera Chryseobacterium, Microbacterium, Salinibacterium, Pusillimonas, Roseomonas, and Janibacter were isolated from water samples. In genomes of Pusillimonas and Roseomonas strains the genes associated with nitrate reduction, resistance to heavy metals and metalloids were revealed. Several isolates are able to participate in the geochemical process of nitrate conversion to N2 using acetate; this results in decreasing redox potential, which in turn may stimulate radionuclide reduction and decrease radionuclide migration in groundwater.

Biotransformation of Neptunium in Model Groundwaters

Abstract—The kinetics of Np(VI and V) reduction was studied in model underground water in the presence of bacteria, isolated from from deep-injection disposal of liquid radioactive wastes of Siberian Chemical Plant. Obtained data indicate a chemical instability of Np(VI) in the studied system. The reduction of neptunium (V) depended on its initial concentration and the presence of microorganisms. In microbiome samples, the reduction rate has significantly increased and neptunium-bearing particles more than 200 nm in size were formed. At neptunium concentrations less than 10–7 М, the reduction rate constant did not depend on the radionuclide content (half-reaction period of 36–40 days). An increase of Np concentration to 10–6 М led to a two-fold decrease of the reduction rate constant.

Uranium uptake with graphene oxide sponge prepared by facile EDTA-assisted hydrothermal process

Seeking highly efficient and low-cost sorbents to removal uranium contaminants is of great concern in demand. In present work, a graphene oxide sponge (GOS) was successfully assembled by a facile Ethylenediaminetetraacetic acid (EDTA)-assisted hydrothermal method from graphene oxide (GO) sheets. The prepared GOS was characterized, and the influencing factors on uranium sorption were optimized. Results indicate that the GOS shows a spongy porous structure and significantly enhances the U(VI) removal compared with the pristine GO. Langmuir model well describes the equilibrium sorption data. Under experimental conditions, the maximal uranium sorption calculated from Langmuir model was found to be 212.77 mg · L−1. Sorption kinetics data are matched with pseudo-second-order model. Reusability experiments indicate that the prepared GOS can be regenerated using dilute acid treatment and be used repeatedly. The simple and low-cost preparation of GOS predicts the potential applications of spongy GO as an effective sorbent for U(VI) capture and also expands the possibility of using graphene-based sorbent in the disposal of liquid radioactive waste. Copyright © 2016 John Wiley & Sons, Ltd.

Практические и научные результаты, природоохранные и этические аспекты 50-летнего опыта захоронения жидких радиоактивных отходов в глубоких геологических горизонтах

Практические и научные результаты, природоохранные и этические аспекты 50-летнего опыта захоронения жидких радиоактивных отходов в глубоких геологических горизонтах

Modern problems of safe disposal of liquid radioactive waste in geological formations: Radiation-chemical transformations and generation of gases

Problems of the technology of liquid radioactive waste disposal into geological formations, of radiation-thermal transformations of waste components, and of safe operation of disposal sites are discussed. The variation with time of the waste activity and temperature near the borehole shaft, and also chemical transformations of waste components, leading to the generation of gases, are described using mathematical modeling. The whole set of the data obtained confirm that the safety of deep waste disposal sites operated in accordance with the modern regulations is quire satisfactory.

Regional flow and transport simulation of liquid radioactive waste disposal at the Siberian chemical combine for long- and super-long-term postinjection periods

Regional groundwater flow and transport models were substantiated for the site of underground disposal of liquid radioactive waste from the Siberian Chemical Combine. The migration of a neutral component and two radionuclides (90Sr and U) in groundwaters was predicted for the long-(1000 years) and super-long-term (10 000 years) periods using the microdispersion and macrodispersion approaches. A local model-insert of the lithological and hydraulic heterogeneity was developed for substantiating the macrodispersion parameters. The simulation results show that, during the long-term period, the contaminated waters will be mainly localized within the injection zone (below buffer horizon IV), and during the super-long-term period about 90% of the total amount of neutral wastes will be discharged into the drainage network, whereas uranium will be fully retained within the disposal site.

Effect of natural advection on stabilization of contaminant plume in natural traps at underground disposal of liquid wastes

The migration of a contaminant from a zone of injection disposal of hazardous liquid waste in a deep-seated aquifer is considered. Because of its higher density, the polluted groundwater will accumulate under the effect of gravity in aquifer dips (depressions). A 2D-model of variable-density groundwater flow is used to determine the conditions under which the gravity force will prevent polluted groundwater from leaving depressions driven by regional current. As the result, such depressions can serve as natural traps for polluted waters. The required conditions are based on simple analytical relationships, derived from the analysis of a theoretical model of variable-density groundwater flow in an inclined confined aquifer. The obtained technique is used to estimate the efficiency of such a trap at the site of injection disposal of liquid radioactive waste from Mining and Chemical Combine in Krasnoyarsk region. The analytical estimates of the trap with the use of the proposed technique are shown to be in good agreement with the results of numerical simulation of contaminant migration.

Assessment of 137Cs and 90Sr fluxes in the Barents Sea

The annual balance of radionuclides inflow/outflow was assessed for 137Cs and 90Sr isotopes in the Barents Sea, taking into account the atmospheric precipitation, inflow from the Norwegian and the White seas, as well as riverine discharge, liquid radioactive waste disposal (LRWD), and outflow to the adjacent seas. The original and published data for the period of 1950–2009 were analyzed. According to the multiyear dynamics (1960–2009), the inflow of 137Cs and 90Sr into the Barents Sea was significantly preconditioned by the Norwegian Sea currents; and precipitation played a major role in the 1950s, 1960s, and in 1986. Currently, the trans-border redeposition of 90Sr prevails over 137Cs redeposition in the Barents Sea, and constitutes about 99% of inflow of each element.

Microbiological processes in the Severnyi deep disposal site for liquid radioactive wastes

Local monitoring of physicochemical, radiochemical, and microbiological parameters was performed in the deep horizons of the Severnyi site used for disposal of liquid radioactive waste (LRW). Analysis of the chemical and radiochemical composition of the wastes and formation fluid revealed that the boundary for migration of radionuclides lagged behind that for nonradioactive waste components (sodium nitrate) and tritium. The physicochemical and radiochemical conditions in deep horizons did not prevent microbial growth. The numbers of microorganisms (aerobic organotrophs, denitrifying, fermentative, sulfate-reducing, and methanogenic) were low, as were the rates of sulfate reduction and methanogenesis; they increased in the waste dispersion zone. The microorganisms from deep horizons were able to produce gases (CH4, CO2, N2, and H2S) from possible waste components. Denitrifying bacteria belonged to different Pseudomonas species and reduced nitrate to dinitrogen under the conditions of pH, salinity, temperature, and radioactivity found in the disposal site. These results suggest the need for control of microbiological processes in deep disposal site for liquid RW.

Polyfunctional microspherical materials for long-term disposal of liquid radioactive wastes

The possibility of immobilizing liquid radioactive wastes into polyfunctional microspherical materials of the block and powdered types is demonstrated. These materials are intended for reprocessing radioactive wastes of different compositions and make it possible to perform a multistage process of conditioning radioactive wastes under relatively mild conditions (at temperatures below 1000°C) with the conversion of water-soluble cesium and strontium compounds into water-insoluble mineral forms in the course of solid-phase transformations. Owing to the aluminosilicate composition of microspherical components of energy ashes (cenospheres), the cenospheres can serve as precursors of aluminosilicate granitoid minerals. Different techniques are proposed and conditions are experimentally determined for transforming precursors into final mineral-like materials of the predicted structure types chosen in the framework of the geoecological approach. The framework structures of aluminosilicates and phosphates thus formed can fix cesium and strontium in the crystal lattice and ensure the geochemical equilibrium between the matrix and incorporating granitoid rocks under conditions of long-term disposal.

Coprecipitation of Pu(IV) with Fe(III) and Cr(III) hydroxides from nitrate-acetate solutions under hydrothermal conditions simulating deep disposal of liquid radioactive wastes

Precipitation of Fe(III), Cr(III), Ni(II), and Mn(II) from nitrate-acetate solutions and coprecipitation of Pu(IV) with Fe(III) and Cr(III) were studied. The degree of precipitation of 80–95% is attained for Fe(III) at 95–200°C and pH>0.5–0.6, and for Cr(III), at T=95°C and pH≥4.0 or T=200°C and pH≥1.0. The phase composition of the precipitates formed by thermal hydrolysis of iron nitrate in model solutions was analyzed. Depending on pH and temperature, the solid phase contains various modifications of Fe2O3, FeOOH, and amorphous phases. Noticeable coprecipitation of plutonium from nitrate-acetate solutions is observed at pH≥4, and it is incorporated in the precipitate only at formation of FeOOH. No coprecipitation of Pu(IV) with Fe2O3 was found. Under the given experimental conditions, plutonium in aqueous solutions occurs in the oxidation state +4 forming monoacetate (or, probably, hydroxo acetate) complexes.

Ecological solution of the problem of handling liquid radioactive wastes LRW (by the example of FSUE SSC RF RIAR)

A sharp reduction of nuclear waste amounts is possible if their elements are considered as source material of atomic complexes – SMAC. The prospect of their possible salvaging will require technological changes and ensuring safety of storage of the material till the need arises. Long experience in deep liquid radioactive waste disposal and accounting, calculations, and motivations demonstrate that a corresponding choice of geological formations makes it possible to abandon liquid radioactive waste solidification and ensure their isolation from environment when the most rigid radiation safety requirements are fulfilled.

Simulation of the Dynamics of Radiation and Temperature Fields with Deep Burial of Liquid Wastes

A mathematical model of the migration of radionuclides and the dynamics of the temperature field with deep disposal of liquid radioactive wastes in deep porous geological formations is presented. The model includes a description of filtration, convective–dispersion mass transport, sorption and desorption of radionuclides by the enclosing rock, radioactive decay, convective heat transfer, and heat conduction. Software, making it possible to perform predictive calculations of the change in the state of a reservoir formation for radioactive wastes, is developed on the basis of the numerical implementation of the model. The results of simulation of the dynamics of the temperature field and the behavior of radionuclides for operation of one injection well in the test area for deep burial of liquid radioactive wastes at the Siberian Chemical Combine are presented.

Dynamic stabilization of heat-generating liquid waste plume in a sloping aquifer

Contaminant transport by groundwater in a sloping aquifer is considered in the case when contaminant plume has a salinity (and density) different from that of the groundwater, and is heat generating. Forced convection is present due to regional groundwater flow and natural convection is also expected to develop due to concentration differences and thermal changes. Such a situation takes place in deep-well disposal of liquid radioactive waste, in which the heat generation is caused by the radioactive decay.Flow and contaminant transport in the aquifer were calculated in 2D approximation in the plane of the aquifer, and the process of heat conduction in confining rocks was described by a 3D model. The set of equations governing flow, heat and mass transfer in the system was solved numerically with use of finite differences technique. Accuracy of numerical solution was checked by comparison with an original analytical solution of the flow problem for concentration-driven convection.It was shown that the influence of the natural convection component could cause acceleration as well as slowing down of the contaminant plume movement depending on system parameters. Results of numerical solution were approximated by a dimensionless analytical expression, which can be used for estimation of the relative impact of different driving forces exerting influence on the contaminant plume movement.

About this title

This Special Publication presents a largely UK persperctive on groundwater contamination, 'warts' and all. It gives the international reader an oppurtunity to assess the standing of British contaminant hydrogeology in the world today. There are also international papers on organic contamination at industrial sites in the USA, minewater pollution from France and data, previously unavailable, from the major liquid radioactive waste disposal operation in Tomsk, Central Siberia. We hope that this compilation will enable both the experienced hydrogeologist and the interested scientist to discover how we have polluted, investigated and attempted to clean up mankind's most precious geological resource-groundwater

Computer Code System DSOCEAN for Assessing the Collective Dose of Japanese due to Radionuclides Released to the Ocean from a Reprocessing Plant

A computer code system DSOCEAN has been developed for assessing the collective dose of Japanese due to radionuclides released to the ocean from a spent nuclear fuel reprocessing plant. This computer code system uses a box model which represents the transfer of radionuclides between boxes of seawater into which the ocean around Japan is divided. The code system consists of a series of three interlinked main computer codes, which estimates the exchange rates of radionuclides between the boxes, the radionuclide concentrations in each box, and the collective dose from various exposure pathways, respectively.By using DSOCEAN, two calculations were carried out to estimate the collective dose from a liquid effluent. One is associated with a routine release of radionuclides from a hypothetical reprocessing plant. The other is an application of the code system to disposal of liquid radioactive waste to the surface water of the ocean. The calculated results identified important radionuclides and exposure pathways.

Computer Code System DSOCEAN for Assessing the Collective Dose of Japanese due to Radionuclides Released to the Ocean from a Reprocessing Plant.

A computer code system DSOCEAN has been developed for assessing the collective dose of Japanese due to radionuclides released to the ocean from a spent nuclear fuel reprocessing plant. This computer code system uses a box model which represents the transfer of radionuclides between boxes of seawater into which the ocean around Japan is divided. The code system consists of a series of three interlinked main computer codes, which estimates the exchange rates of radionuclides between the boxes, the radionuclide concentrations in each box, and the collective dose from various exposure pathways, respectively.By using DSOCEAN, two calculations were carried out to estimate the collective dose from a liquid effluent. One is associated with a routine release of radionuclides from a hypothetical reprocessing plant. The other is an application of the code system to disposal of liquid radioactive waste to the surface water of the ocean. The calculated results identified important radionuclides and exposure pathways.

New Sorbents and Technologies for Liquid Radioactive Waste Management

ABSTRACTThe possibilities for using various technologies for liquid radioactive waste (LRW) management were considered. Technologies based on the application of sorbents highly selective to radionuclides were shown to have good prospects. Possible ways of increasing selective sorbent efficiency in cleaning radionuclide-polluted waters of various types were examined. The results of studying new high-selective sorbents produced in the Institute of Chemistry FEDRAS are given. The use of these sorbents enables one to treat LRW of various types in a single stage. The results of testing a sorption filter installation for management of LRW produced during operation, repair and disposal of nuclear reactors are presented. Use of this installation resolves a major portion of LRW disposal problems.

One-stop shopping

US patents documents on CD-ROM, a personal densitometer, a beta counter that eliminates the need for liquid radioactive waste disposal, and a blot visualization spray — what's new and what's hot in the scientific product line.