WATER RESISTANCE OF SOLIDIFIED RADIOACTIVE WASTE

The results of experimental studies of leaching characteristic of liquid radioactive waste of radionuclides from cement matrices for long-term storage are considered. It is shown that leach ability is a characteristic of the chemical resistance of matrices, indicating the ability of the matrix material to prevent the spread of radionuclides localized in them into the environment. It is noted that the rate of leaching of radionuclides from cement matrices changes with the time of their contact with aqueous media. Chronometric dependences of leaching rates are presented and analysed. It is shown that they consist of two sections of different duration. The initial section, lasting up to 250 hours, is distinguished by a higher steepness with a decrease in the absolute value of the speed to 2 orders of magnitude. The subsequent section, lasting up to 2500 hours or more, is characterized by an asymptotic decrease in speed to a constant minimum value. Approximating functions of the experimental chronometric dependences of radionuclide leaching were obtained in the form of power-logarithm expressions, valid in the intervals of the duration of the experiments, with a reliability of at least 0.9. It is shown that monovalent sodium and cesium ions are most intensively subject to leaching. The absolute values of the rates of leaching of monovalent nuclides are two to three orders of magnitude higher than those of divalent ones, all other things being equal. The content of the nuclide in the composition of the compound material has a significant effect on the leaching rate. An increase in matrix temperature promotes an increase in leaching rates, which is most likely due to a positive temperature coefficient of diffusion characteristics. Irradiation of the matrices decreases the leaching rate as a result of a decrease in the porosity of the matrix body and the formation of poorly soluble hydrates. The redox values of matrix-bound solutions have no significant effect on the leaching rate.

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Influence of Geopolymer Binder Components on Properties of Compounds during Cementation of Boron-Containing Liquid Radioactive Waste

Nuclear Power and the Environment ◽

10.31717/2311-8253.21.2.7 ◽

2021 ◽

Vol 21 (2) ◽

pp. 71-77

Author(s):

Yu. G. Fedorenko ◽

◽

Yu. A. Olkhovyk ◽

A. N. Rozko ◽

G. P. Pavlyshyn ◽

...

Keyword(s):

Radioactive Waste ◽

Liquid Glass ◽

Potassium Hydroxide ◽

Linear Equations ◽

Liquid Radioactive Waste ◽

Correlation Coefficients ◽

Component Composition ◽

Normative Values ◽

Leaching Rate ◽

Base Compound

The paper presents an analysis of the experimental results of the use of geopolymer binders for cementing boron-containing liquid radioactive waste (LRW). The dependence of the properties of compounds on the component composition of binders has been studied. The following components are considered: liquid glass with a silicon modulus of 2.9, a mixture of ash of Darnytsya TPP with slag of the Mariupol metallurgical plant in a ratio of 1: 1 and potassium hydroxide. To perform a factor analysis of the effect, the mass of these substances was taken as three factors in the analysis at two levels. For the manufacture of compounds imitation LRW was mixed with zeolite in a ratio of 10:1 at a temperature of about 60 оC. Subsequently, the above components were added to the mixture, the weight of which varied by ±17% relative to the weight of the base compound. To study the properties, samples of different sizes 5×5×5 cm, 1.5×1.5×1.5 cm and rectangular samples with an outer surface from 96 cm2 to 104 cm2 were made. Each property was studied in 8 samples. The obtained results allowed to construct linear equations that quantitatively link the corresponding characteristic of the compound with the composition of the binders. The correlation coefficients between the experimental and the data calculated by the equation are estimated. The average values of the correlation coefficients may indicate that not all factors were taken into account. The obtained regularities show that in the conditions of the experiment slag and ash increase, and liquid glass and potassium hydroxide reduce the rate of setting of the samples. The density of the samples is increased by ash and slag, while liquid glass and potassium hydroxide are reduced. The compressive strength of liquid glass and potassium hydroxide is reduced, while the mixture of ash and slag is increased. The leaching rate Сs of liquid glass and potassium hydroxide is increased, the mixture of ash and slag is reduced. At the same time, the leaching rate of Sr increases the ash/slag mixture, while liquid glass and potassium hydroxide decrease. The time during which the leaching of Cs reaches the normative values, slag and ash are reduced, and liquid glass and potassium hydroxide are lengthened. The obtained results can be taken into account when optimizing the composition of geopolymer binders for cementing LRW.

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Use of mathematical modeling to extend the scope of application for the procedure of measuring the mass of 235U in solid radioactive waste

Nuclear Energy and Technology ◽

10.3897/nucet.5.36478 ◽

2019 ◽

Vol 5 (2) ◽

pp. 163-169

Author(s):

Nikita S. Rykov ◽

Gennady M. Bezhunov ◽

Vyacheslav M. Gorbachev

Keyword(s):

Radioactive Waste ◽

Mass Measurement ◽

Matrix Material ◽

Measurement Range ◽

Spectrometric Method ◽

Standard Samples ◽

Absolute Efficiency ◽

The Matrix ◽

Scope Of Application ◽

Solid Radioactive Waste

The known dependence of absolute efficiency on energy and space for particular measurement conditions is used to determine the mass (activity) of 235U in solid radioactive waste by gamma-spectrometric method. The ISOCS system makes it possible to avoid laborious and time-consuming calibration measurements using standard samples to obtain the absolute efficiency curve due to using the so-called characterized detector having a file with a set of efficiencies for various measurement geometries. In many cases, the establishment of standard samples with parameters covering the 235U mass measurement range in the variation intervals of influencing factors, including density, non-uniformity, isotopic composition, geometry, etc., is very expensive and, most often, not feasible. With regard for this, a computational and experimental approach is used based on results obtained by Monte Carlo method using the MCNP code with variation of the key influencing parameters in a broad range. Calculations were performed for detector-recorded spectra of gamma quanta from casks containing waste differing in the density of the cask content (the density was calculated with regard for the uranium contained in waste) – from 0.016 to 1 g/cm3, in the mass of uranium in waste – from 0.64 g to 2 kg, and in the matrix material – graphite, cellulose, quartz, cellulose with 20 % of iron dust. Applicability boundaries have been defined for the developed procedure to measure uranium-containing waste in terms of the material matrix (~ 2.2 %) and its density (~ 10 %) and the contribution of the uranium mass uncertainty in the cask (5 % for nonporous matrices, 10 % for porous matrices) to the obtained result has been estimated.

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Development of the matrix material selection algorithm for immobilization of transurane elements using the modified method of analysis of hierarchies

Nuclear and Radiation Safety ◽

10.32918/nrs.2018.2(78).06 ◽

2018 ◽

pp. 36-42

Author(s):

E. Skiter

Keyword(s):

Radioactive Waste ◽

Material Selection ◽

Matrix Material ◽

Synthesis Method ◽

Synthesis Methods ◽

Technological Parameters ◽

Matrix Synthesis ◽

Radiation Chemical ◽

Transuranium Elements ◽

The Matrix

The method of selecting the matrix material and the matrix synthesis method for immobilizing radioactive waste containing transuranium elements was developed using a system approach. A decomposition of the task of selecting and evaluating the selection parameters at different levels of the hierarchy has been carried out. An algorithm for solving the choice problem is proposed on the basis of the modified hierarchy analysis method. It is shown that the use of this algorithm in the selection of the matrix material makes it possible to take into account its radiation-chemical, physico-mechanical properties and technological parameters of the matrix synthesis methods, which makes it possible to make a motivated choice of the matrix optimal for immobilization of radioactive waste containing transuranium elements.

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Advanced Vitreous Wasteforms for Radioactive Salt Cake Waste Immobilisation

MRS Advances ◽

10.1557/adv.2020.45 ◽

2020 ◽

Vol 5 (3-4) ◽

pp. 121-129

Author(s):

Vladimir A. Kashcheev ◽

Nikolay D. Musatov ◽

Michael I. Ojovan

Keyword(s):

Radioactive Waste ◽

Liquid Radioactive Waste ◽

Synthesis And Characterization ◽

Cold Crucible ◽

Leaching Rate ◽

Salt Cake ◽

Solid Salt ◽

Cement Compound

AbstractSalt cake radioactive waste is a remnant solid salt concentrate after deep evaporation of radioactive evaporator concentrate at WWER NPP’s. The traditional cementing of borate-containing liquid radioactive waste, to which the salt cake belongs, leads to a significant increase in the volume of the final product. This work describes borosilicate vitreous wasteforms developed to immobilize radioactive salt cake waste and comprises data on both glass synthesis and characterization. The composition of glass selected for the purpose of immobilisation of the salt cake radioactive waste allows to include up to 40 wt. % of the oxides contained in the salt cake and to reduce the volume of the final product by more than 2 times compared with the cement compound. The batches were melted in a cold crucible melter at 1200 °C. The normalized cesium leaching rate of the vitrified wasteform product was within range 3.0·10-5 – 3.7·10-6 g/(cm2·day).

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Liquid Radioactive Solidification Technologies

Nuclear and Radiation Safety ◽

10.32918/nrs.2019.1(81).12 ◽

2019 ◽

pp. 68-74 ◽

Cited By ~ 1

Author(s):

V. Svidersky ◽

V. Glukhovsky ◽

I. Glukhovsky ◽

T. Dashkova

Keyword(s):

Radioactive Waste ◽

Nuclear Power ◽

Power Plants ◽

Liquid Radioactive Waste ◽

Cement Stone ◽

Leaching Rate ◽

Additional Water ◽

Volumetric Characteristics ◽

Leaching Parameters ◽

The Cost

This review provides a brief analysis of familiar and tested technologies of liquid radioactive waste solidification. The technologies of bituminization, vitrification and incorporation of radioactive waste into the polymer matrix are considered. The paper presents the efficiency indices of the conventional cementation technology and sets forth the results of calculating the cost of components for cementing liquid radioactive waste of various concentrations. Besides, there are results of calculating the volumetric characteristics of cement stone for water-cement relations used for cementing liquid radioactive waste. The review includes the results based on the development and implementation of solidification technologies for liquid radioactive waste using contact-hardening binders that form a durable waterproof stone at the time of pressing and do not require additional water for curing. Generated compounds for immobilization of liquid radioactive waste from nuclear power plants are tested to identify their strength characteristics, resistance to irradiation and leaching parameters. The paper covers the calculation of the cost of components for the solidification of liquid radioactive waste of various concentrations. The developed technology of liquid radioactive waste solidification allows obtaining compounds with strength up to 40 MPa. The volume of the final product is increased by 1.8 times, and the leaching rate is in the range of 1.10×10–4…9.5×10–5 kg/m2 per day.

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Exloring the Characteristics of Backfill Materials Proposed for Well Decommissioning Purposes at the Site of Zheleznohorsk Liquid Radioactive Waste Deep Disposal Facility

Radioactive waste ◽

10.25283/2587-9707-2021-2-63-72 ◽

2021 ◽

Vol 15 (2) ◽

pp. 63-72

Author(s):

A. V. Ponizov ◽

◽

A. P. Pustovgar ◽

A. N. Dorofeev ◽

P. M. Vereshchagin ◽

...

Keyword(s):

Radioactive Waste ◽

Water Resistance ◽

Defect Formation ◽

Liquid Radioactive Waste ◽

Aqueous Media ◽

Aquatic Environments ◽

Protective Properties ◽

Factors Affecting ◽

Disposal Facility ◽

Backfill Materials

The paper focuses on Portland cement and cement-bentonite mixture-based backfill materials presenting the results of studies performed to assess the influence of factors affecting their performance and protective properties considering the conditions inherent for the Zheleznogorsk liquid radioactive waste deep disposal facility. The following factors were considered as the key ones: type of the backfill material; chemical composition of the impacting aquatic environments in the injection horizons; temperature of aqueous media containing heat-generating radionuclides. During the study, specified was the influence of these factors on the following protective properties of the formed backfill stones: strength, water resistance, tendency to defect formation. The results obtained can be used to develop closure designs for the Zheleznogorsk LRW DDF.

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Polishing process effect on the image of dispersed precipitates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112646 ◽

1984 ◽

Vol 42 ◽

pp. 534-535

Author(s):

C.T. Hu ◽

C.W. Allen

Keyword(s):

Matrix Material ◽

Specimen Preparation ◽

Second Phase ◽

Precipitate Particle ◽

Polishing Process ◽

Second Phase Particles ◽

The Matrix ◽

Surface Profiles ◽

Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

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Application of cross correlation to HREM images of surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128080 ◽

1987 ◽

Vol 45 ◽

pp. 754-755

Author(s):

D. E. Luzzi ◽

L. D. Marks ◽

M. I. Buckett

Keyword(s):

Cross Correlation ◽

A Priori ◽

Matrix Material ◽

Correlation Method ◽

Accurate Knowledge ◽

Complex Image ◽

Fourier Filtering ◽

The Matrix ◽

Low Pass ◽

Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

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