Development of dual phase magnesia-zirconia ceramics for light water reactor inert matrix fuel

Dual phase magnesia-zirconia ceramics were developed, characterized, and evaluated as a potential matrix material for use in light water reactor inert matrix fuel intended for the disposition of plutonium and minor actinides. Ceramics were fabricated from the oxide mixture using conventional pressing and sintering techniques. Characterization of the final product was performed using optical microscopy, scanning electron microscopy, x-ray diffraction analysis, and energy-dispersive x-ray analysis. The final product was found to consist of two phases: cubic zirconia-based solid solution and cubic magnesia. Evaluation of key feasibility issues was limited to investigation of long-term stability in hydrothermal conditions and assessment of the thermal conductivity. With respect to hydrothermal stability, it was determined that limited degradation of these ceramics at 300^oC occurred due to the hydration of the magnesia phase. Normalized mass loss rate, used as a quantitative indicator of degradation, was found to decrease exponentially with the zirconia content in the ceramics. The normalized mass loss rates measured in static 300^oC de-ionized water for the magnesia-zirconia ceramics containing 40, 50, 60, and 70 weight percent of zirconia are 0.00688, 0.00256, 0.000595, 0.000131 g/cm2/hr respectively. Presence of boron in the water had a dramatic positive effect on the hydration resistance. At 300^oC the normalized mass loss rates for the composition containing 50 weight percent of zirconia was 0.00005667 g/cm2/hr in the 13000 ppm aqueous solution of the boric acid. With respect to thermal conductivity, the final product exhibits values of 5.5-9.5 W/(m deg) at 500^oC, and 4-6 W/(m deg) at 1200^oC depending on the composition. This claim is based on the assessment of thermal conductivity derived from thermal diffusivity measured by laser flash method in the temperature range from 200 to 1200^oC, measured density, and heat capacity calculated using rule of mixtures. Analytical estimates of the anticipated maximum temperature during normal reactor operation in a hypothetical inert matrix fuel rod based on the magnesia-zirconia ceramics yielded the values well below the melting temperature and well below current maximum temperatures authorized in light water reactors

Fuel performance modeling results for representati

The objective of the present study was to predic

Fuel performance modeling results for representati

The objective of the present study was to predic

Highly Variable Active Galactic Nuclei in the SRG/eROSITA All-Sky Survey: I. Constructing Sample and Catalog of Sources Detected in Low State

We present the results of our search for highly variable active galactic nuclei (AGNs) the X-ray flux from which changed by more than an order of magnitude during the SRG/eROSITA all-sky survey. Using the eROSITA data obtained in the period from December 2019 to February 2022, we have found 1325 sources the X-ray flux from which in the 0.3-2.3 keV energy band changed by more than a factor of 10 at a confidence level of at least 99.73 %. Of them, 635 objects have been classified as AGNs or AGN candidates. We describe the procedure of searching for highly variable sources and the selection of extragalactic objects among them and describe the statistical properties of the produced catalog. We provide a catalog of 49 sources for which a statistically significant flux in their low state was detected. For the latter we provide their light curves and X-ray spectra and discuss in detail the most interesting of them.Comment: 9 figures, 2 table

On the Groundstate of Yang-Mills Quantum Mechanics

A systematic method to calculate the low energy spectrum of SU(2) Yang-Mills quantum mechanics with high precision is given and applied to obtain the energies of the groundstate and the first few excited states.Comment: 4 pages REVTEX twocolumn, no figures; important calculational mistake corrected which considerably changes the conclusions; references adde

AFIP-6 Breach Assessment Report

Analysis of the AFIP-6 experiment is summarized in this report in order to determine the cause of gaseous fission product release observed during irradiation. During the irradiation, a series of small fission product releases were observed. In order to limit the potential for primary coolant contamination, the operating cycle was terminated and the AFIP-6 experiment was removed for examination. Both in-canal and post-irradiation examination revealed the presence of an unusually thick oxide layer and discrete surface blisters on the fuel plates. These blisters were the likely cause of fission product release. Subsequent detailed thermal hydraulic analysis of the experiment indicated that the combination of the high operating power and test vehicle configuration led to high nominal operating temperatures for the fuel plates. This elevated temperature led to accelerated surface corrosion and eventually spallation of the fuel plate cladding. The thermal insulating nature of this corrosion layer led to significantly elevated fuel meat temperatures that induced blistering. Analysis was performed to validate a corrosion rate model and criteria for onset of spallation type surface corrosion were determined. The corrosion rate model will be used to estimate the oxide thickness anticipated for experiments in the future. The margin to the spallation threshold will then be used to project the experiment performance

Transmutation Fuel Performance Code Conceptual Design

One of the objectives of the Global Nuclear Energy Partnership (GNEP) is to facilitate the licensing and operation of Advanced Recycle Reactors (ARRs) for transmutation of the transuranic elements (TRU) present in spent fuel. A fuel performance code will be an essential element in the licensing process ensuring that behavior of the transmutation fuel elements in the reactor is understood and predictable. Even more important in the near term, a fuel performance code will assist substantially in the fuels research and development, design, irradiation testing and interpretation of the post-irradiation examination results

Analysis of the “sustainable development” concept

The article presents the results of the study of the essence and specificity of the term "sustainable development", as well as the development of its author's vision in modern realities. Currently, sustainable development is one of the key trends in the development of the world. At the same time, it affects almost all aspects of society and the state. It is explained by the fact that it is based on three important areas: economic, environmental and social. However, there are both opponents and supporters of the concept of sustainable development. The greatest success in implementation in practice and scientific results have been achieved by researchers in developed foreign countries: Europe, USA, Japan, etc. At the same time, there is no unified position in the essence and peculiarities of such a complex interdisciplinary category. The purpose of this work was to develop an adequate approach to assessing the modern interpretation of the term "sustainable development". The study is based on the work of many domestic and foreign authors. The main method of work is analytical. The results obtained -a detailed analysis of the development of approaches to the studied terminology, allowed us to formulate the author's current approach to this concept

Thermal Modeling of A Friction Bonding Process

A COMSOL model capable of predicting temperature evolution during nuclear fuel fabrication is being developed at the Idaho National Laboratory (INL). Fuel plates are fabricated by friction bonding (FB) uranium-molybdenum (U-Mo) alloy foils positioned between two aluminum plates. The ability to predict temperature distribution during fabrication is imperative to ensure good quality bonding without inducing an undesirable chemical reaction between U-Mo and aluminum. A three-dimensional heat transfer model of the FB process implementing shallow pin penetration for cladding monolithic nuclear fuel foils is presented. Temperature distribution during the FB process as a function of fabrication parameters such as weld speed, tool load, and tool rotational frequency are predicted. Model assumptions, settings, and equations are described in relation to standard friction stir welding. Current experimental design for validation and calibration of the model is also demonstrated. Resulting experimental data reveal the accuracy in describing asymmetrical temperature distributions about the tool face. Temperature of the bonded plate drops beneath the pin and is higher on the advancing side than the retreating side of the tool

Transmutation Fuel Performance Code Thermal Model Verification

FRAPCON fuel performance code is being modified to be able to model performance of the nuclear fuels of interest to the Global Nuclear Energy Partnership (GNEP). The present report documents the effort for verification of the FRAPCON thermal model. It was found that, with minor modifications, FRAPCON thermal model temperature calculation agrees with that of the commercial software ABAQUS (Version 6.4-4). This report outlines the methodology of the verification, code input, and calculation results