Cementitious materials will be very important structural elements of a deep geological repository, but they can be used also as a part of engineering barriers. A$~$comparative study of radium and strontium uptake by different cementitious materials was therefore performed. Three cementitious materials were studied: a$~$hardened cement paste (HCP CEM II) and two types of concrete (Concrete CEM...
Decomposition of aqueous solutions of uranyl nitrate in a matrix of granulated silica gel (KSKG grade) under the action of microwave radiation (MWR) was studied. Microwave irradiation leads not only to formation of solid decomposition products UO3, UO2(OH)NO3, and their hydrates in pores of KSKG granules, but also to accumulation of gaseous NOx and H2O. The presence of NOx in KSKG pores leads...
The crucial agents in partitioning of high level liquid nuclear waste are organic ligands capable of selective complexation of the actinides and lanthanides. To evaluate their applicability, it is necessary to study the stability against undesirable reactions of these ligands, causing their structural changes. One of the main cause for degration is represented by reactions with highly...
Operation of the nuclear power plant is accompanied by the radioactive contamination of internal and external surfaces of equipment. Usually, the main part of surface contamination of the equipment's nuclear power plant is due to activated corrosion products. Decontamination of removable equipment can be done in various ways, depending on its size and design features. Electrochemical...
Currently proposed concepts for safe isolation of radioactive wastes imply development of a multibarrier system which consists of both natural and engineered barriers. Hosting rock of depository serves as a natural barrier. It appears for already-existing depositories and disposal facilities. It is naturally chosen on the stage of disposal development. Vertical and horizontal curtains of...
Most of the migration data for radium in the performance assessment of deep geological repository, which are used in modelling the long-term safety, were obtained from experiments performed with its chemical analogues - barium and strontium. To our knowledge, there are few data available on radium migration in the engineered barrier of compacted bentonite, possibly due to difficult work with...
It is required to secure decontamination technology that is easy to apply and minimizes the generation of secondary wastes for large-scale equipment and large-area decontamination, which are difficult to be applied structurally when massive repair or decommissioning of nuclear facilities. In this respect, decontamination foam has a potentially wide application in the removal of contaminants...
Thorough understanding of the aqueous complexation of U(VI) with ubiquitous inorganic ligands, such as hydroxide and carbonate, is crucial for predicting U(VI) mobility in natural and engineered systems, since retardation processes largely depend on the metal speciation. U(VI) hydrolysis [1] and complexation with carbonate in weakly alkaline media [2] have been extensively studied. This work,...
Vast territories with soils contaminated by radionuclides (RN) and/or mercury have appeared as a result of anthropogenic accidents, long-term activity of mining and processing plants, heat power plants, nuclear fuel cycle industry, as well as a consequence of decommissioning of such objects. These contaminants easily get involved to migration processes in the environment and frequently cause...
Future nuclear fuel cycles based on fast reactors are being developed in many countries. New nuclear fuel cycles include the reduction of long term radiotoxicity of nuclear waste by partitioning and transmutation of long lived transplutonium elements. So the selective recovery of transuranium elements, especially actinides (III) – americium and curium, from the high lever radioactive waste...
Inner and outer safety barriers are constructed when decommissioning nuclear fuel cycle facilities takes place. Combination of different barriers prevents leakage of radionuclides and other pollutants into environment.
The outer barriers formation in geological media is carried out by injection method that allows one to minimize significance of hosting rocks contribution for depositories...
The main goal of the project Development of tools for Studying Contaminant Transport in fractured rock environment (TH02030543; 2lsConTra), funded by Czech Technology agency, is to develop tools for evaluation of migration and retention of potential contaminants in the rock environment as the key input values the safety assessment of anthropogenic activities. Those may release contaminants...
Diffusion and sorption of radionuclides in veined gneiss from Olkiluoto, Finland
H. Aromaa(1), M. Voutilainen(1), J. Ikonen(1), M. Yli-Kaila(2) and M. Siitari-Kauppi(1)
(1)Department of Chemistry, University of Helsinki, P.O. Box 55, 00014 University of Helsinki, Finland
(2) Posiva Oy, Olkiluoto, 27160 Eurajoki, Finland
A project “rock matrix REtention PROperties” (REPRO) at ONKALO, the...
Over the last decades, membrane methods (especially reverse osmosis) have been increasingly used for treatment of liquid radioactive waste (LRW). The reverse osmosis methods are most efficiently used in combination with microfilters and ion exchange filters. Based on experience of using the NITI-designed modular sorption membrane system (MSMS) in LRW treatment and concentration process, an...
Experimental work within the CEBAMA project focuses on alteration and interaction studies on cementitious materials (based on Portland type CEM II, w:c = 0.45, OPC) in contact with groundwater (GW) from Underground Research Facility Josef and with bentonite suspension (Czech B75 bentonite) in pressure vessels during three sampling campaigns (9/18/27 months) under in-situ (10°C) and high...
Bentonote clays are widely used as engineering barrier materials for radioactive waste disposal into geological formations due to their low permeability, considerable sorption capacity in relation to radionuclides, good swelling ability, heat resistance, thermal conductivity. Nowdays several bentonites deposits in Russia and
CIS countries are currently being developed that are Zyryanskoe...
Iodine radionuclides largely define radiation hazard at nuclear power plants under both normal operation and emergency. The factors that determine the high level of potential hazard of iodine are its volatility and a possibility to remain in various physical and chemical forms such as iodide (I-), molecular (I2), iodine organic, for example, methyl iodide (CH3I), iodate (IO3-) or periodate...
Mineral-like magnesium-potassium-phosphate (MPP) compound samples were synthesized during the immobilization of a high level waste (HLW) simulator. The phase composition and structure of compounds were studied and their physico-chemical properties, including mechanical and thermal stability, were determined. The high hydrolytic stability of the MPP compound was established: the differential...
Selenium-79 (79Se) is one of the important long-lived fission products exists in radioactive waste and has toxic anionic species in an aqueous environment. Consequently, 79Se is considered as a key radionuclide that should be taken into consideration in safety assessments in radioactive waste repository. Commenly, the usage of bentonite as a buffer material is suggested in radioactive waste...
Nowadays computer models of fuel fabrication/refabrication, SNF reprocessing and waste management processes are under development as part of technologies front-end and back-end of closed fuel cycle. One of them is software package “VIZART” [1,2]. Code “VIZART” is used for material flow calculations of technological schemes and dynamic calculations of equipment work, taking into account...
Dissolution of corrosion layers is strongly connected with the problem of decontamination and decommissioning of nuclear facilities, which has become of the current issues in many countries. The key process to decontaminate metals, is to dissolve surface corrosion layer and remove radionuclides. From corrosion studies on the surface of stainless steel under primary circuit conditions of...
Foam decontamination process has a potentially wide application in the removal of contaminants from large components with complex shapes or large area or large volumes. This process can be applied to any direction regardless of walls, floors and ceilings, and basically it has the advantage of generating less secondary wastes. However, there is a disadvantage that the decontamination factor...
Recent years some alternative techniques are being developed for solid state matrixes producing for immobilisation of liquid and mixed state radioactive wastes. Magnesium-potasium-phosphorus ceramics (MPP ceramics) matrix are considered to be a promising solid state matrix for immobilisation of liquid and mixed state radio-active wastes as alternative to cement and glass matrix. The major...
In the current time the task of management the accumulated volumes of irradiated graphite obtained by uranium-graphite reactors decommission (over 250,000 tons in the world) is acute in Russia along with other countries. It is known during the reactors operation the carbon and chlorine present in the nuclear graphite become activated. Besides various incidents during reactor exploitation occur...
The extraction system that supposed to be used for extraction of radionuclides must have suitable extraction and hydrodynamic characteristics, as well as to be explosive- and fire-safe in operation. The main reason of the worsening the circulating extractant quality is the formation and accumulation of various organic compounds under irradiation. The main products of radiolytic degradation in...
Reprocessing of spent nuclear fuel became the key issues for the environmentally friendly and sustainable development of nuclear energy. For the future development of nuclear energy requirements, the concept of an accelerator-driven advanced nuclear energy system (ADANES) has been proposed in China. ADANES consists of a burner system and a fuel recycle system. The waste transmutation,...
In The Czech Republic a selection of locality for deep repository of spent nuclear fuel is currently in progress. For the safety evaluation it is necessary to verify that the radionuclides penetrating the engineered barriers and a geosphere are not reaching a biosphere in high concentrations. Flow123D and GoldSim SW are used for the solute transport simulations in a geosphere. The advantage of...
The post-accident measure demand has raised after Fukushima Daichi accident. One of the main challenges was related to treatment of large volumes of the highly radioactive waste waters, being generated during the severe accident mitigation. Therefore UJV Řež in the cooperation with CEZ, a.s. and Slovenské elektrárne, a.s. has started to review the concept and potential design of radioactive...
To evaluate the retention potential of the concrete barrier in a nuclear waste repository towards actinides in the presence of high saline water, leaching experiments with actinide-doped calcium silicate hydrate (CSH) phases were performed in highly saline electrolytes. Therefore, U(VI)- and Cm(III)-doped CSH phases with different C/S ratios (1.0-2.0) were synthesized directly in presence of...
In order to develop resins with selectivity to U(VI) in HNO3 media, we have synthesized several polymer beads with the structure of a monoamide as the functional group. For wider applications of these resins including treatment of highly-radioactive solutions, it is necessary to investigate their stability under irradiation conditions. In this study, resins with a chain-type monoamide and a...
Radioactive wastes, especially high-level waste (HLW) and intermediate-level waste (ILW), generated predominantly in nuclear fuel cycles contain a wide variety of radionuclides including long-term radionuclides and the wastes contain also various chemicals, often complexation agents used for decontamination purposes. Due to the presence of large quantities of long-term radionuclides, HLW and...
In the technological system of high-burnt irradiated nuclear fuel reprocessing that is being developed, before entering the affination phase, all the reductant from the previous phase of reducing reextraction must be deconstructed and the Pu(III) must be oxidized to Pu(IV). For this process a reagentless oxidation method using an activated carbon catalyst (VNIITU-1) was proposed. As a result...
The effect of dissolved hydrogen on the oxidative dissolution of highly Pu-doped MOX and externally irradiated UO2
Nuclear Chemistry/Industrial Materials Recycling, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
Swedish Nuclear Fuel and Waste Management Co., SE-101 24 Stockholm, Sweden
The release of radiotoxic species from future final geological nuclear waste...
Investigation of causes of the accidents, leading to explosions and fires at nuclear facilities, is an important component in ensuring nuclear and radiation safety because of the significant impact of such accidents on the personnel, population and environment. Among a large num-ber of nuclear facilities, the most dangerous are SNF reprocessing plants, which are currently using processes such...
During reprocessing of spent nuclear fuel by PUREX process uses an extractant that consist of a mixtures of TBP in a light hydrocarbon diluent. In the Russian industrial practice mainly used saturated aliphatic hydrocarbons, but currently discusses the possibility of using branched-chain hydrocarbons, which have advantages properties over the first. Because in the technology process extractant...
We present on the development of the Micro-Optical Ring Electrode (MORE) for the analysis of trans-uranium elements in aqueous mixtures. The MORE is a photo-electrochemical device based on a ring microelectrode that uses the insulator interior to the ring as a light guide. This single device exploits the unique photophysical and electrochemical properties of multiple analytes present in...
Long-term controlled storage or disposal is one of the major stages of liquid radioactive waste (LRW) management. The preparation of LRW for this stage includes the conversion of waste into a stable solidified form. In recent years, researches devoted to the development of new methods of LRW solidification are carried out using a magnesium-potassium-phosphate (MPP) compound based on the...
The work describes an experimental study of the determination of chemical stability of protective coatings under conditions of severe accidents at nuclear power plants. Another task of the work was to evaluate the thermal degradation of the coatings and the analysis of the resulting solids (debris), which can cause overload of cooling systems, as well as be a source of release of combustible...
Cementing methods is mainly used for low and intermediate level radioactive waste. Currently, cement stone is almost never considered as a matrix for immobilizing high level waste due to probable low durability of as well as to radiolysis cement hydrates and pore-water under high radiation dose.
The objective of this report is the assessment of cement compounds affected by high radiation dose...
Samples of the zeolite clinoptilolite, mined from Mud Hills in California, have been tested in column experiments to determine their ability to remove radioactive Cs+ and Sr2+ ions. The clinoptilolite was effective in removing both Cs+ and Sr2+ from aqueous solution. Increasing concentrations of Ca2+, Mg2+, Na+ and K+ competed with the Cs+ and Sr2+, and increased elution of Cs+ and Sr2+. Ca2+,...
One of the ways for diminishing risks during storage and burial of Purex-process HLW, which are arising from high heat evolution by -emitting 90Sr & 137Cs, is recovery of long-lived TPE radio-nuclides, especially 241+243Am, which could be recycled in NFC by inclusion in the fuel for fast reac-tors. Commercial TPE partitioning in Russia has been carried out and developed using fluorinated...
Liquid radioactive waste (LRW) represent serious environmental problem due to their multicomponent composition: presence of long-lived radionuclides with variable oxidation states as well as nitrate ion in high concentrations. One of the most problematic types of LRW are alkaline waste generated in the PUREX process of spent nuclear fuel recovery. Annually are generated about 6490 m3 of...
One of the prospective directions in the development of the generation IV reactors is the use of liquid metals as a coolant. At the same time, to ensure compliance with all the requirements, it is necessary to solve many practical problems and challenges. The subject of this work are radiochemical investigations required for licensing of the MYRRHA reactor conducted within the MYRTE-project...
