Electrodeposition of chromoxide coatings from electrolytes modified with SiO₂·nH₂O

To increase the corrosion resistance of stainless steel from local types of corrosion, chromium oxide coatings obtained from electrolytes modified with SiO₂·nH₂O were applied to its surface. It has been established that the coatings obtained from the electrolyte with the addition of SiO₂·nH₂O are continuous, without cracks, and finely crystalline compared to the coating obtained from the base electrolyte. Elemental analysis did not show the presence of silicon in the composition of the coating obtained from the modified SiO₂·nH₂O electrolyte, however, it showed the presence of a larger amount of chromium compared to the coating obtained from the base electrolyte. On the polarization curves, there is a complication of the release of hydrogen at the cathode and oxygen at the anode, which indicates a decrease in the electrical conductivity of the obtained coatings. The results obtained make it possible to recommend the use of SiO₂·nH₂O additives to the electrolyte to obtain chromium oxide coatings on steel with enhanced corrosion protection properties.Для підвищення корозійної стійкості нержавіючої сталі від локальних видів корозії на її поверхню нанесли хромоксидні покриття, отримані з електролітів, що модифіковані SiO₂·nH₂O. Встановлено, що покриття з електроліту з додаванням SiO₂·nH₂O є суцільними, без тріщин, та дрібнокристалічними у порівнянні з отриманим покриттям з базового електроліту. Елементний аналіз не показав наявності силіцію у складі покриття, який отриманий з модифікованого SiO₂·nH₂O електроліту, проте показав наявність більшої кількості хрому в порівнянні з покриттям, отриманим з базового електроліту. На поляризаційних залежностях спостерігається ускладнення виділення водню на катоді, та кисню на аноді, що свідчить про зниження електропровідності отриманих покриттів. Дані результати дозволяють рекомендувати використання добавки SiO₂·nH₂O до електроліту для отримання на сталі хромоксидних покриттів з підвищеними захисними властивостями від корозії

Corrosion resistance of traditional and advanced fuel rod cladding materials for water-cooled reactors

The available literature experimental data on corrosion resistance of traditional and advanced fuel rod cladding materials for water-cooled reactors are summarized. A review of zirconium alloys, which have proven themselves in operation for more than half a century, is presented. As noted, the research work is constantly being carried out to improve zirconium alloys by optimizing their composition, in particular, the amount of tin, niobium, iron and oxygen, as well as development of the new alloys. First of all, the direction of these works is stimulated by stringent nuclear energy requirements, including maximum safety, efficiency and environmental friendliness. At the same time, in the last decade, one of the main goals of researchers around the world is the development of nuclear fuel systems, which tolerate severe accidents. Another trigger for this was the accident in 2011 in Japan at the Fukushima-1 NPP

Corrosion Resistance of Traditional and Advanced Fuel Rod Cladding Materials for Water-Cooled Reactors

The available literature experimental data on corrosion resistance of traditional and advanced fuel rod cladding materials for water-cooled reactors are summarized. A review of zirconium alloys, which have proven themselves in operation for more than half a century, is presented. As noted, the research work is constantly being carried out to improve zirconium alloys by optimizing their composition, in particular, the amount of tin, niobium, iron and oxygen, as well as development of the new alloys. First of all, the direction of these works is stimulated by stringent nuclear energy requirements, including maximum safety, efficiency and environmental friendliness. At the same time, in the last decade, one of the main goals of researchers around the world is the development of nuclear fuel systems, which tolerate severe accidents. Another trigger for this was the accident in 2011 in Japan at the Fukushima-1 NPP. As the most optimal possible solution, it is considered the surface modification of zirconium alloys by the development of chromium coatings. Such coatings provide an increased corrosion resistance and wear resistance, as well as hydrogen pickup reduced at operating temperatures of the primary coolant and in emergencies. A more radical way to increase the fuel rod cladding accident resistance is to replace the zirconium alloy with another one. The best candidates are FeCrAl alloys and duplex stainless steels (DSS), whose corrosion resistance can be 50 times greater than that of zirconium alloys in loss-of-coolant accident (LOCA) conditions. Unfortunately, under the nominal water-cooled reactor operating conditions, a long-term operation such as claddings will lead to the corrosion product formation and its removal to the coolant followed by their activation and formation of deposits in the core and steam generator. This will certainly entail an increase in the radiation-dose rate from the primary circuit equipment. Considering the traditional and advanced water-cooled reactors claddings, which tolerate severe accident scenarios, an optimized zirconium alloy with chromium coating can be considered as the most advanced one. The corrosion resistance of such claddings is at least five times higher compared to traditional zirconium alloys both under normal operating conditions and severe accidents, and will not cause significant neutron absorption, coolant activation or deposit formation in the primary circuit