Papers by Keyword: Zirconium Alloy

Abstract: Nuclear power plants (NPPs) result in accumulation of a significant amount of radioactive products during the process of their storage and the presence of a potential release of radioactive products, in the case of an accident that is a source of potential hazard and risk of radiation impact on the personnel, population and environment in general. The paper shows the microgalvanic corrosion element formed on the inner wall of fuel rods made of Zr + 1%Nb alloy and pellets made of uranium oxides, as well as the outer galvanic element of fuel rods and structural materials of the reactor made of steel of different grades. The hazards caused by corrosion damage and release of hazardous radioactive substances from the reactor based operating area are analyzed. The possibility of predicting the rate of corrosion damage using a mathematical model on the thermodynamic approach is determined and established.

Abstract: One of the factors limiting the operation time of nuclear reactor is corrosive wear of the reactor core structural materials and fuel element cladding due to continuous action of water coolant. Thus, for VVER (water-water energetic reactor) type reactors, local galvanic corrosion, which occurs between the surface of fuel element cladding made of zirconium alloy and various grade steel parts of other structural elements is peculiar. A short-circuited galvanic cell formed on the inner wall of Zr + 1% Nb alloy fuel elements is shown. Changes in oxide films thicknesses depending on the time at different water medium acidity are analyzed. A generalized model demonstrating that dissimilar metals in the reactor core (zirconium alloy and steel) form a short-circuited galvanic cell, resulting from which an increase in local corrosion of zirconium alloy occurs is presented.

Abstract: The paper deals with experimental data regarding the effect of internal and external factors on the corrosion decay of Zr1Nb alloy fuel elements. Based on the analysis results, losses of zirconium that transfers to oxide or coolant as per the fuel element wall weight and thickness as well as economic losses from their corrosion decay have been theoretically calculated. To avoid a state-level emergency occurrence, an increase in the fuel element wall thickness up to 660 μm is proposed, which can increase the operating life under the conditions of trouble-free coolant mass transfer hydrodynamic mode.

Abstract: The comparative study of Ga⁺ ion, Nb⁺ ion, proton and electron (H⁺ and e^-) irradiation on single crystal and poly crystal Zirconium (Zr), characterised in terms of misorientation profile change, EBSD maps or microtexture, XRD residual stresses development and irradiation hardening effect. It was concluded that the rate of damage is varying with respect to irradiation source. In the present study both the Zr and its alloys were used to conclude this main objective.

Abstract: In this work, the total mass attenuation coefficient and partial interactions of the zirconium alloy have been calculated by WinXCom program at 1 keV-100 MeV gamma ray energies. Zr₂(Fe,Ni) alloys was studied for the mass attenuation coefficients, photoelectric absorption, incoherent, coherent and pair production processes. The effective atomic numbers and electron densities were also calculated. The calculated results show that the total mass attenuation coefficient decreased with increasing of gamma rays energy. The value of total mass attenuation coefficient of each material was different, which depend on chemical compositions of alloy. The partials interactions, effective atomic numbers and electron densities were also calculated and discussed.

Abstract: Experimental Stand for Testing Electrochemical Permeation (STEP) of hydrogen through metal foils was constructed and described in this paper. Hydrogen diffusion coefficients in different metal foils at room temperature can be determined by using STEP. Influence of pulsed electron beam irradiation on hydrogen diffusion coefficient in zirconium alloy E110 was investigated. It was established that treatment by pulsed electron beam with the energy density of 18 J/cm², by three impulses with duration 50 μs leads to a decrease in the diffusion coefficient of hydrogen on the order of one. This is due to the fact that structure with more branched crystals’ boundary formed after irradiation and such structure is effective trap for hydrogen. Also there is formation of protective oxide film after irradiation.

Abstract: Hydrogen sorption, structural phase state and mechanical properties after hydrogenation of zirconium alloy Zr1%Nb with ZrO₂ and TiO₂ coatings were investigated. It has been established that ZrO₂ coating reduces the rate of hydrogen sorption by zirconium alloy Zr1%Nb in comparison with the initial material at hydrogen saturation temperature 450 °С.

Abstract: When used commercially, the zirconium alloys are utilized in the shape of tubes to encapsulate the UO2 pellets in the PWR and BWR Power reactors. The metallic zirconium is an essential metallic element for the types of alloys in which the obtainment route rests in the ore opening for the production of zirconium oxide followed by the processes of pelletizing, chlorination, purification, reduction and distillation. Through the technique of X-Ray Diffraction the present phases were identified. Using the Fluorescence of an X ray it was possible to determined the chemical composition of the zirconium sponge. The mechanical properties of Vickers microhardness were obtained using a microdurometer. As a result, it was established that it is possible to define a methodology for the preparation of a sample of metallic zirconium for the microstructure analysis, as well as that its chemical purity is 97,265% linked to the microhardness of approximately 51 HV.

Abstract: The jewelry making has been traditionally considered handcrafted and hinged on the ability of goldsmiths to create components and assemblies. In recent years, however, a profound transformation has begun, driven by the global markets requiring robust engineering approaches to the analysis of new materials and of product/process optimization. Moreover, gold and silver were conventionally associated to the jewelry production, but the use of materials other than precious metals (such as steels, titanium alloys, woods and ceramics) is nowadays a standard for many companies. In this context, the research activities presented and described in this paper focus on the performance evaluation of a Zirconium alloy, in terms of material properties and machinability, for the application in the jewelry industry. Perspiration, salt spray and abrasion tests provided results comparable or even superior to those typical of a Ti-6Al-4V alloy, especially in case a Zirconia layer is induced on the Zirconium alloy through a properly designed oxidizing treatment. Machinability can be performed with conventional tools and equipment, and the production route of jewel prototypes is detailed.

Abstract: Zirconium alloys are widely used in the nuclear industry because of their relative high strength, neutron transparency, resistance to high neutron-irradiation environment and corrosion resistance. One application for Zirconium alloy Zr-2.5Nb is the vacuum confinement vessel utilised in the cold neutron source of the OPAL research reactor at ANSTO. Having a total length of more the 3 meters, it is made of two sections joined using electron beam welding. The weld and the nearby regions are critical for the performance and integrity of the component and therefore understanding of the residual stresses development within the weld is important in connection to (i) evolution of fine dual phase α/b microstructure and crystallographic texture (ii) and stress-related radiation induced phenomena, such as grain growth, creep and sub-critical crack growth by delayed hydride cracking. The stresses were measured in and around an electron beam weld produced during the development of this component of the OPAL Cold Neutron Source. The effects of a large grain size in the weld were reduced by taking advantage of rotational symmetry and rotating the sample to increase the swept volume. Due to the heat-treatment after welding, the stresses were very low, less than 10% of the yield strength of the material, in both the hoop and axial directions. As a result of phase transformation effects during the welding process the final stresses are compressive in the weld, which reduces the likelihood of fracture or of hydride formation in this region. The highest stresses are in the parent material adjacent to the weld where the toughness is expected to be higher than in the weld material.