Solidification of intermediate-level liquid wastes with the use of inorganic binders
Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Cited by 4 publications
References 0 publications
The results of work on the development of the process regime for cementing salt concentrates from the Volgodonsk nuclear power plant are presented. Experiments on model and real bottoms residues from liquid-wastes storage tanks show that additionally concentrating the wastes and regulating the alkalinity can yield cement compounds with dry residue content up to 30% percent. Portland and slag portland cement can be used as the binding material. When the conditions which have been determined are met, the quality of the cement compounds formed meets all normative requirements. The recommended process regime has been implemented in the cementing facility at the Volgodonsk nuclear power plant.The main condition for the development of nuclear power is safe operation of nuclear power plants. One factor which can cause radioactive contamination of the environment is storing liquid radioactive wastes on the territory of a plant. According to currently operative normative documents, liquid radioactive wastes, including from nuclear power plants, must be converted into a solid form that ensures the safety of long-term storage and burial of the wastes. Until recently, commercial facilities for solidifying salt concentrates operated in our country only at the Leningrad and Kalinin nuclear power plants. The bitumenization technology is used to condition liquid wastes at these plants. Commercial test operation of its cementing facility developed at SverdNIIkhimmash is now in operation at the Volgodonsk nuclear power plant to solidify concentrates of bottom wastes. The main technological unit of this facility is a bulk mixer which operates periodically, producing cement compounds that can be stored in a container -a 200 liter metal barrel.Before commercial cementing was adopted at the Volgodonsk nuclear power plant, the process parameters ensuring reliable operation of the equipment and production of a cement compound with the highest possible degree of filling, the quality of which meets the requirements of the established normative documents (GOST R 51883-2002 and NP-019-2000), were developed. According to these requirements, the mechanical strength of the cement compounds under compression must be at least 50 kg/cm 2 (4.9 MPa), be characterized by radionuclide leach rate not exceeding 10 −3 g/(cm 2 ·day), and possess satisfactory water-resistance and freezing-resistance.In addition to the normative requirements for the quality of the cement compounds, there are also technical requirements which ensure accident-free operation of the facility. Specifically, the plasticity of the cement slurry must ensure that the slurry is completely removed from the apparatus and fills the container well (the flowability of the cement slurry, deter-
The results of work on the development of the process regime for cementing salt concentrates from the Volgodonsk nuclear power plant are presented. Experiments on model and real bottoms residues from liquid-wastes storage tanks show that additionally concentrating the wastes and regulating the alkalinity can yield cement compounds with dry residue content up to 30% percent. Portland and slag portland cement can be used as the binding material. When the conditions which have been determined are met, the quality of the cement compounds formed meets all normative requirements. The recommended process regime has been implemented in the cementing facility at the Volgodonsk nuclear power plant.The main condition for the development of nuclear power is safe operation of nuclear power plants. One factor which can cause radioactive contamination of the environment is storing liquid radioactive wastes on the territory of a plant. According to currently operative normative documents, liquid radioactive wastes, including from nuclear power plants, must be converted into a solid form that ensures the safety of long-term storage and burial of the wastes. Until recently, commercial facilities for solidifying salt concentrates operated in our country only at the Leningrad and Kalinin nuclear power plants. The bitumenization technology is used to condition liquid wastes at these plants. Commercial test operation of its cementing facility developed at SverdNIIkhimmash is now in operation at the Volgodonsk nuclear power plant to solidify concentrates of bottom wastes. The main technological unit of this facility is a bulk mixer which operates periodically, producing cement compounds that can be stored in a container -a 200 liter metal barrel.Before commercial cementing was adopted at the Volgodonsk nuclear power plant, the process parameters ensuring reliable operation of the equipment and production of a cement compound with the highest possible degree of filling, the quality of which meets the requirements of the established normative documents (GOST R 51883-2002 and NP-019-2000), were developed. According to these requirements, the mechanical strength of the cement compounds under compression must be at least 50 kg/cm 2 (4.9 MPa), be characterized by radionuclide leach rate not exceeding 10 −3 g/(cm 2 ·day), and possess satisfactory water-resistance and freezing-resistance.In addition to the normative requirements for the quality of the cement compounds, there are also technical requirements which ensure accident-free operation of the facility. Specifically, the plasticity of the cement slurry must ensure that the slurry is completely removed from the apparatus and fills the container well (the flowability of the cement slurry, deter-
621.039.7 As in most countries, in our country the concept of burial of low-and medium-level wastes near the surface, i.e., in burial sites located on the earth's surface or at a shallow depth, has been adopted for solidification of such wastes [1][2][3][4]. The solidified wastes placed in such burial sites can be influenced by a change in the composition of the water in contact with them, the variable temperature, the presence of microbiological action, and other factors.Radionuclides escape into the environment mainly because the solidified wastes come into contact with water, which can enter the burial site as a result of a leak in the site. In the process both ground water and surface water (rain or flood waters) can penetrate into the site. In addition, as the water passes through the shielding barriers, it will be enriched by the soluble components of the constructional and biospheric materials.A great deal of attention is being devoted to the study of the factors which influence the behavior of the solidified wastes stored near the surface or in the case of accidents during shipment [5][6][7].The effect of the composition of the contact water on the rate of leaching of the most mobile element -cesium from cement and bitumen compounds, which were obtained during solidification of salt concentrates formed during the operation of nuclear power plants with VVI~R and RBMK reactors, has been studied under laboratory conditions. The cement compounds were prepared using a mixture of Portland cement and bentonite clay in the ratio 9:1. The content of the dry residue of the wastes in the compound was equal to 15 and 30% for wastes from nuclear power plants with RBMK and VVI~R reactors, respectively. Distilled water [8], water which for a period of one month was in contact with the bentonite clay employed in burial sites as a buffer material, or with fragmented hard concrete, and water containing macrocomponents of the wastes leached out of the cement compounds were used as the leaching medium (Table 1). The rate of leaching of the cesium was determined by the method adopted in [8]. The investigations were performed on samples in the form of 8 cm 3 cubes.The results indicated a very small change in the amount of cesium arriving in the leach medium during the time of the experiment. The fraction of 137Cs leached out of the compounds with salt concentrates of a nuclear power plant with a RBMK reactor over a period of 159 days is equal to 3-7% for distilled water and 3-5 % for water in contact with the bentonite clay.Approximately 8% of the 137Cs in the distilled water, 7.5-8% in the water in contact with the bentonite, 11-12% in the water in contact with the hard concrete, and about 9% in the ground water was leached from the cement samples with salt concentrates from a nuclear power plant with a VVI~R reactor over a period of 14 days. As one can see, in this case the difference in the leach rate does not exceed 50%.Another factor that can affect the escape of radionuclides from cement compounds into the environmen...
Cementing, i.e., incorporating liquid radioactive wastes into inorganic binders (Portland cement, Portland blastfurnace cement, metallurgical slags), is the simplest and cheapest method of conditioning. However, this method also has 11 drawbacks, one of which is that it is impossible to decrease or even increase the volume when cementing liquid radioactive wastes with salt content of up to 200 g/liter [1]. In this case, the salt content in the solidified wastes is 5-7%.Preliminary investigations on model compositions have shown that cementing can produce quite hard materials, containing up to 26 and 19% dry residue of salt concentrates from nuclear power plants with RBMK and VVI~R reactors, respectively. The hardness under compression of such materials is much higher than 100 kg(force)/cm 2 [2].The determination of the water resistance of cemented materials with a high salt content on 137Cs-marked samples has shown that after 14 days the rate of leaching of t37Cs from the samples containing 15% dry residue from the wastes from a nuclear power plant with a RBMK reactor is 1"10 -4 g/(cm2'day), and the leach rate from samples with 33% dry residue of the wastes from a nuclear power plant with a VVER reactor under the same conditions is I. 10 -3 g/(cm2"day). These preliminary results have shown that it is in principle possible to obtain cement materials with a higher salt content than previously thought [I].To confirm the possibility of obtaining cement compounds with a high salt content, investigations were performed with real concentrates. For this, salt concentrates from nuclear power plants with a VVI~R (Novovoronezh, Kalinin, and Zaporozh'e) and RBMK (Kursk) reactors and wastes from the Scientific and Industrial Association "Radon," a large fraction of which consist of distillation residues of liquid wastes from scientific-research institutes, were performed.As one can see from the data in Table I, the mass of the dry residue from the RBMK nuclear power plant (Kursk) and the Scientific and Industrial Association "Radon" consist mainly of sodium nitrate and the wastes from the VVER nuclear power plant contain, together with sodium nitrate, a large quantity of sodium borates, whose content in the wastes from different stations is different.To ensure a high degree of filling of the cement materials, the salt content of the liquid radioactive wastes must be increased by additionally concentrating them. This is achieved by obtaining high-salt concentrates on the UGU-500 deepevaporation plant (Novovoronezh and Zaporozh'e nuclear power plants) or evaporation of real solutions under laboratory
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
Contact Info
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Product
Resources
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.
