Corrosion of simulated nuclear waste glass

Glasses are suitable host matrices for the immobilization of high-level radioactive wastes. The corrosion behaviour of nuclear waste glass in water is of considerable importance, since a potential route for returning of radionuclides to the biosphere is their leaching from the waste form into groundwater and subsequent transport by the groundwater to the surface. In this study, the preparation and characterization of borosilicate glasses of different chemical composition were investigated. Borosilicate glasses were doped with simulated nuclear waste oxides. The chemical corrosion in water of these glasses was followed by measuring the leach rates (g·cm^–2·day^–1), as a function of time. It was found that a simulated nuclear waste glass with the chemical composition (weight %), 15.61% Na₂O, 10.39% B₂O₃, 45.31% SiO₂, 13.42% ZnO, 6.61% TiO₂ and 8.66% waste oxides, is characterized by low melting temperature and with good corrosion resistance in water. Influence of passive layers on the leaching behaviour of nuclear waste glasses is discussed.     

Dissolution behavior of MgO-P2O5 glass system for vitrification of high-level radioactive waste

Journal of Radioanalytical and Nuclear Chemistry - The MgO-P2O5 glass system exhibits atypical behavior in the relationship between physical properties around the metaphosphate composition...     

Preparation and characterisation of glass product with modified composition for vitrification of high level radioactive waste

During the vitrification of high level radioactive liquid waste (HLW) at advanced vitrification system (AVS) in Tarapur, the glass forming chemicals are introduced into the melter in the form of preformed glass frit, known as base glass. A five component system, SiO₂–B₂O₃–Na₂O–Fe₂O₃–TiO₂ is presently used as the base glass at AVS. Towards the step to product improvement, a modified base glass composition with seven components, SiO₂–B₂O₃–Na₂O–CaO–Fe₂O₃–TiO₂–K₂O was formulated with reduced boron content and incorporation of mixed alkali elements Na and K as compared to presently adopted base glass composition. The modification was mainly aimed at reducing boron volatilization during vitrification without affecting the present state of product quality to improve melter life and to some extent take advantage of mixed alkali effect. The modified base glass and product glass based on modified base composition were evaluated for different properties with respect to existing composition. The fusion and pouring temperatures were well with in the range of plant requirement. The glass transition temperature, coefficient of thermal expansion and thermal conductivity were similar or better. The product glass was having good homogeneity and chemical durability.     

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include ³H, ¹⁴C, ³⁶Cl, ⁴¹Ca, ^59,63Ni, ^89,90Sr, ⁹⁹Tc, ¹²⁹I, ^135,137Cs, ²¹⁰Pb, ^226,228Ra, ²³⁷Np, ²⁴¹Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.     

Use of EGD for the characterization of fining processes of glass melt

The control and optimization of the glass-making process is a serious problem in glass production. An EGD procedure involving high-temperature vacuum extraction and total pressure measurement allows determination of the fining state (Läuterzustand) and fining behaviour (Läuterverhalten). The fining state is characterized by the contents of CO₂, N₂ and other gases from the batch reactions, and gas inclusions. Oxygen evolved in a second step is characteristic for the fining behaviour.

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Zusammenfassung Die Kontrolle und Optimierung des Gasgehaltes von Glasschmelzen ist eine wichtige Voraussetzung für eine gleichbleibende Qualität der Glasprouktion. Eine EGD-Technik mit Hilfe der Hochvakuumheißextraktion und Gasdruckmessung erlaubt, den Läuterzustand und das Läuterverhalten einer Glasprobe zu bestimmen. Der Läuterzustand wird durch die Gase aus den Gemengereaktionen und Gemengeeinschlüssen (CO₂, N₂ u. a.) bestimmt. Das Läuterverhalten ergibt sich aus der Menge des in einer zweiten Stufe extrahierbaren Sauerstoffs.

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The use of emanation thermal analysis for the investigation of radioactive waste fixation processes

The process of incorporation of radioactive wastes into a suitable matrix to form a stable product for long term disposal has been studied. The changes, occuring during the thermal treatment with glassy materials, i.e. drying, transformation processes, sintering, melting, etc. have been followed using emanation (radon) thermal analysis. This method was found useful in solving the problems of process development.     

A radiometric method for the determination of non-ionic surfactants

A radiometric method for the determination of non-ionic surfactants of ethylene oxide type has been elaborated. The principle of the method is the formation of an associate¹³³Ba-non-ionic surfactant — dicarbolide and its extraction into a mixture nitrobenzene-chloroform /41/. The extracted activity of¹³³Ba is proportional to the non-ionic surfactant concentration in the sample. The factors influencing the determination of non-ionic surfactants in the real waste solution after washing have been studied. The possibility of the determination of non-ionic surfactants by the calibration graph method and by the method of standard addition was verified.     

Substoichiometric method in the simple radiometric analysis

The substoichiometric method is applied to simple radiometric analysis. Two methods-the standard reagent method and the standard sample method-are proposed. The validity of the principle of the methods is verified experimentally in the determination of silver by the precipitation method, or of zinc by the ion-exchange or solvent-extraction method. The proposed methods are simple and rapid compared with the conventional superstoichiometric method. The University has moved and changed its name and address as lollows: Institute of Chemistry, The University of Tsukuba 300-31 Sakura-mura, Ibaraki Japan.     

Radiochemical analysis of radionuclides difficult to measure for waste characterization in decommissioning of nuclear facilities

Some radiochemical analytical methods for the determination of important beta-radionuclides for decommissioning are presented. An analytical method is briefly described, which is used for the determination of ³H and ¹⁴C in steel and aluminum by combustion using commercial oxidizer. A leaching method was developed for the determination of ³H in the contaminated silica gel. A simple distillation method is presented for the determination of ¹⁴C in heavy water and wastewater sample. A method developed for the simultaneous determination of ³H, ¹⁴C, ³⁶Cl, ⁵⁵Fe, ⁶³Ni, ⁴¹Ca and ¹²⁹I in concrete, graphite, aluminium, lead, and steel is presented. The developed methods have been successfully used to analyse various materials for characterization of the waste during the decommissioning of Danish nuclear reactors.     

Intrinsic dosimetry of glass containers: a potential interrogation tool for nuclear forensics and waste management

Intrinsic dosimetry is the method of measuring total absorbed dose received by the walls of a container holding radioactive material. By considering the total absorbed dose received by a container in tandem with the physical characteristics of the radioactive material housed within that container, this method has the potential to provide enhanced pathway information regarding the history of the container and its radioactive contents. We report the latest in a series of experiments designed to validate and demonstrate this newly developed tool. Thermoluminescence (TL) dosimetry was used to measure dose effects on raw stock borosilicate container glass up to 70 days after gamma ray, X-ray, beta particle or ultraviolet irradiations at doses from 0.15 to 20 Gy. Two main peaks were identified in the TL glow curve when irradiated with ⁶⁰Co, a relatively unstable peak around 120 °C and a more stable peak around 225 °C. Signal strength of both peaks decayed with time. The minimum measurable dose using this technique is 0.15 Gy, which is roughly equivalent to a 24 h irradiation at 1 cm from a 50 ng ⁶⁰Co source. As a result of fading, this dose would be detectable for approximately 1 year post-irradiation. In a more detailed analysis, the TL glow curves were separated into five peaks centered near 120, 160, 225, 300, and 340 °C. Differences in TL glow curve shape and intensity were observed for the glasses from different geographical origins. These differences can be explained by changes in the intensities of the five peaks. This suggests that mechanisms controlling radiation induced defect formation from gamma, beta, X-ray, and UV sources may be similar.     

A new method for determining the radon emanation coefficients and radon production rates in different building materials using solid state nuclear track detectors

Radon α-activity concentrations have been measured inside and outside various building materials by combining a calculational method with the solid state nuclear track detector (SSNTD) technique. Radon emanation coefficients of the studied materials have been evaluated. A new calibration method for determining the radium (²²⁶Ra) and thorium (²³²Th) specific activities of the considered building materials has been developed. The radon production rates per unit volume of the studied materials have been evaluated. The influence of the material porosity on the radon emanation coefficient and radon production rate have been investigated.     

Use of indigenous microwave system for dissolution and treatment of waste from nuclear materials

Microwave heating technique has the unique advantages of low processing time, less consumption of reagents, homogeneous heating and maintenance-free adaptability to glove box. Dissolution of thorium and plutonium containing fuel viz sintered thorium oxide, thorium-uranium oxide and thorium-plutonium oxide pellets is one of the most difficult step for their analysis and characterization. Complete dissolution of the fuel samples is a pre-requisite for the analysis of fuel material in the solution form. Even a trace level of un-dissolved particle may interfere with the accurate and precise determination in the analysis. Large volumes of liquid and solid wastes are generated during the processing and analysis of samples. These wastes being radioactive can’t be disposed directly to sea or soil. They have to be segregated and categorised and all possibilities are explored to see the feasibility of retrieving the precious nuclear material. The present paper describes an overview of all the efforts made at AFFF for rapid dissolution of nuclear materials using an indigenous microwave digestion system as well as its use for the treatment of waste being generated.     

Application of instrumental radioanalytical techniques to nuclear waste testing and characterization

This paper describes the validation of a multi-technique analytical methodology that uses inductively coupled plasma-mass spectrometry, α-spectrometry, and γ-spectrometry for the routine analysis of samples containing transuranic radionuclides. This methodology is capable of the determination of concentrations of both²³⁸Pu and²⁴¹Pu in the presence of²³⁸U and²⁴¹Am without the need for chemical separations. The relative merits of these three techniques were evaluated as they are applied in a nuclear waste material and spent nuclear fuel testing program by analytical (1) standards and (2) solutions prepared from the dissolution of glasses doped with²³⁷Np,²³⁹Pu, and²⁴¹Am. The uncertainty associated with technique was within ±4% for standards and ±10% for doped nuclear waste glasses. The methodology was then used to analyze three fully radioactive waste glasses.     

Laboratory standard for radionuclides in nuclear waste

A laboratory standard for the determination of long-lived radionuclides in nuclear waste has been prepared using concrete as matrix. It will be used to check sample preparation procedures, chemical separations and methods for the determination of nuclides, e.g., nuclear counting techniques or mass spectrometry. The material chosen was a fine-grained ready-to-use cement mixture, to which the following radionuclides were added:⁶⁰Co and¹³⁷Cs as -ray-emitting nuclides,⁹⁹Tc,⁹⁰Sr and⁵⁵Fe as radionuclides emitting pure -radiation or low-energy electrons, and²³³U,²³⁷Np,²³⁸Pu and²⁴¹Am as -emitters. Care was taken to attain a homogeneous distribution of the nuclides in the standard material. Pieces of about 1 g were formed as suitable and representative samples. Repeated analyses were carried out with the standard to check its homogeneity. The analytical procedures are described in brief. The pieces of the standard material have the same content of nuclides within ±5% at a 95% level of confidence.     

Use of emanation thermal analysis in the study of thermal behaviour of inorganic materials

Emanation thermal analysis [1, 2] (ETA) is based on the measurement of the inert gas release from samples previously labelled. The high detection sensitivity of radioactive nuclides used for the measurement makes it possible to use very low concentrations of the inert gases (10^–14 at %) so that no influence of the inert gases on the properties of the solids can be supposed.

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Zusammenfassung Emanations — Thermoanalyse [1, 2] (ETA) basiert auf der Messung von freigesetztem inerten Gas aus zufor markierten Proben. Die große Nachweisempfindlichkeit der bei der Messung verwendeten radioaktiven Nuklide ermöglicht die Anwendung sehr niedriger konzentrationen (10^–14 Atom%) für das inerte Gas. Somit kann angenommen werden, daß die Eigenscahften des Feststoffes durch das inerte Gas nicht beeinflußt werden.

     

Analytical calculation of the collimated detector response for the characterization of nuclear waste drums by segmented gamma scanning

Improved methods for the reconstruction of the isotope specific activity content in nuclear waste drums with data obtained by a gamma scanning system developed at Shanghai Jiao Tong University require an analytical function of the detector response. In this work we derive an analytical detector response function for a collimated HPGe detector with a square collimation window. The model is based on a purely geometric model respecting the configuration of the collimated detector system, the positions of radioactive point sources and the absorption of γ-rays in the matrix as well as in the HPGe crystal. We show that the derived analytical detector response function is in good agreement with data simulated by MCNP5.     

Synthesis and characterization of surrogate nuclear explosion debris: urban glass matrix

Journal of Radioanalytical and Nuclear Chemistry - We report a study of a fast radiochemical method to determine the activity of 131I via the radiochemical recovery obtained with a 129I tracer....     

A modified radiometric method for plutonium determination in irradiated fuel

A modified radiometric method for the determination of plutonium in irradiated nuclear fuel is described. The analysis consists of total plutonium alpha-activity, activity ratio²³⁸Pu:(²³⁹Pu+²⁴⁰Pu) and burnup determination. The error of plutonium determination is practically identical with that of a classical radiometric method. The method suggested is suitable for large sample series of the same type of irradiated nuclear fuel.     

A new method for studying the influence of pollution and soil nature on the radon emanation from water samples by using solid state nuclear track detectors

Radon emanation from surface water and groundwater samples has been studied by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). A calibration method for determining the thoron and radon concentrations of the water samples studied has been developed. The effect of pollution due to coal fly ashes, cement and granite dusts on the radon emanation from water samples has been investigated. The influence of the radon source on the radon emanation rates from water samples has been studied.