Study of the Solid-State Synthesis of Nickel Ferrite (NiFe2O4) by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Raman Spectroscopy

Spinel ferrite compounds continue to receive a lot of attention due to their unique properties. Among the numerous synthesis routes existing, the solid-state method was applied for the production of nickel ferrite, by introducing the use of a quartz vial. A mixture of nickel oxide (NiO) and hematite (Fe2O3) was ground and vacuum-sealed in the vial and different thermal treatment programs were tested. The resulting particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. For temperatures, below 1000 °C, the solid-state reaction is not complete as nickel oxide (NiO) and hematite (Fe2O3) are still present. The reaction time is a decisive parameter for the morphology of the particles obtained. If, for different reaction times, the particle size distribution is always between 0.3 and 1.7 µm, a longer reaction time leads to the formation of dense, interconnected clusters of particles. Optimal parameters to synthesize a pure phase of spherical nickel ferrite were sought and found to be a reaction temperature of 1000 °C for 72 h

Modeling particle deposition in the primary circuit of pressurized water reactors for the OSCAR code

International audienceParticulate corrosion products are generated in the primary system of pressurized water reactors (PWRs) by volume precipitation and by erosion of oxides formed on metal surfaces through their uniform corrosion. The activation of corrosion products, mainly 58Co and 60Co (respectively coming from the activation of 58Ni and 59Co) leads to radiation field growth around the primary system, directly impacting system integrity and the radioprotection of nuclear workers. In order to understand and mitigate contamination by activated corrosion products, contamination predictions can be performed using the OSCAR code, which relies on the development of models to describe the numerous and complex interactions at stake. Particulate corrosion products account for a significant portion of corrosion products, as such the deposition/erosion mechanisms have their importance for the overall computation of surface or volume contamination. The aim of this article is to present an updated and inclusive deposition model for particulate corrosion products by taking into account surface interactions. The impact of the new deposition model on contamination predictions is then evaluated and has enabled to reproduce, for the first time using the OSCAR code, the preferential contamination in 58Co in the cold side of the circuit, measured by gamma spectrometry with the EMECC device on commercially PWRs

Study of the solid-state synthesis of nickel ferrite (NiFe2O4) by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy.

International audienceSpinel ferrite compounds continue to receive a lot of attention due to their unique properties. Among the numerous synthesis routes existing, the solid-state method was applied for the pro-duction of nickel ferrite, by introducing the use of a quartz vial. A mixture of nickel oxide (NiO) and hematite (Fe2O3) was ground and vacuum-sealed in the vial and different thermal treatment programs were tested. The resulting particles were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Raman spectroscopy. For temperatures, below 1000 °C, the solid-state reaction is not complete as nickel oxide (NiO) and hematite (Fe2O3) are still present. The reaction time is a decisive parameter for the morphology of the particles obtained. If for different reaction times the particle size distribution is always be-tween 0.3 and 1.7 µm, a longer reaction time leads to the formation of dense, interconnected clus-ters of particles. Optimal parameters to synthesize a pure phase of spherical nickel ferrite were sought and found to be a reaction temperature of 1000 °C for 72 hours

Magnetite (Fe3O4) and nickel ferrite (NiFe2O4) zeta potential measurements at high temperature: Part II – Results, study of the influence of temperature, boron concentration and lithium concentration on the zeta potential

International audiencePredicting the deposition of typical corrosion products (CPs) particles formed in the primary system of pressurized water reactors (PWRs) is important for system integrity and the radioprotection of nuclear workers. Such corrosion products foul heat transfer surfaces, promote localized corrosion and, when made radioactive in the reactor core, transport throughout the coolant system and give rise to radiation fields around components. Accurately predicting CPs’ propensity to transport and deposit around the system entails knowing their zeta potentials, quantities that until now have been unavailable. The zeta potentials of magnetite and nickel ferrite particles between 20 °C and 240 °C have been measured in the chemical conditions representative of an operating cycle of the primary system of PWRs. The measurements were performed via the streaming potential method as described in a previous paper – Part I. The measured values increased with temperature but decreased with increasing concentrations of boron and lithium. They are suitable for predicting radiation field growth around components of a typical PWR system

Simulation of Co-60 uptake on stainless steel and alloy 690 using the OSCAR V1.4 code integrating an advanced dissolution-precipitation model

International audienceThe contamination of a nuclear cooling system by activated corrosion products (ACPs) is a process that involves many different mechanisms all interacting with each other. One of the most important mechanisms is dissolution-precipitation. This governs the transfer of soluble corrosion products between the circulating water and the immobile oxidized surfaces, and is strongly dependent on the water chemistry. The dissolution-precipitation model was improved in version 1.4 of the OSCAR computer code, which simulates the ACPs transfer in nuclear reactor systems. The OSCAR v1.4 code is now able to better calculate the incorporation of minor species (e.g., a cobalt isotope) into oxides using the chemistry module, PHREEQCEA, which determines the composition of an ideal solid solution and the equilibrium concentrations of elements in the aqueous solution. This model was challenged by comparing the results obtained using OSCAR v1.4 with the experimental results of a test performed in a dedicated loop by Studsvik Nuclear AB. Finally, with this model, the OSCAR v1.4 code accurately reproduces soluble $^{60}$Co uptake on stainless steel and alloy 690 under various experimental conditions (pH, Zn injection and flow rate)