Корозійна стійкість оболонок твелів виробництва компанії «Westinghouse» під час експлуатації в умовах водно-хімічного режиму ВВЕР-1000. Визначення енергії активації корозії цирконієвого сплаву та верифікація розрахункової моделі

• Дата: 2023
• Автори: Zuyok, V., Tretyakov, M., Rud, R., Kushtym, Ya., Grytsyna, V., Solovyov, Yu., Kulyk, Ye.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: State Scientific and Technical Center for Nuclear and Radiation Safety 2023
• Онлайн доступ: https://nuclear-journal.com/index.php/journal/article/view/1042
• Назва журналу: Nuclear and Radiation Safety

The paper presents the results of a range of activities to determine the corrosion resistance of Westinghouse fuel cladding made of ZIRLO® alloy during operation for four fuel cycles in VVER-1000 reactors of Ukrainian NPPs. An array of experimental results was obtained and systematized to determine the thickness of the oxide film according to the cladding height of fuel rods, and it was shown that the maximum oxide thickness after the fourth year of operation is within 13...25 μm. The corrosion condition of fuel cladding outer surface was assessed and the relation between the surface appearance and oxide film thickness was determined during the visual inspection. The obtained results of the oxide film thickness measurements on the surface of fuel cladding made of ZIRLO® alloy are below the maximum limit (60 μm) established at the design stage and when obtaining a permit for fuel operation in the core, as well as significantly below the maximum design limit (<101.5 μm) for ZIRLO® alloy cladding. According to the results of measurements carried out at PNPP Unit 3 and ZNPP Unit 5, it can be asserted that fuel cladding made of ZIRLO® alloy possess high corrosion resistance under the conditions of the Ukrainian VVER‑1000 primary water chemistry. The corrosion activation energy of the ZIRLO® alloy was determined upon the results of the oxide thickness measurements for fuel cladding at PNPP Unit 3 and ZNPP Unit 5, as well as calculated operating parameters under the conditions of the VVER-1000 core. The corrosion activation energy value of the ZIRLO® alloy is 27280 cal/mol for VVER-1000, which is higher than for Western PWR reactors (27080 cal/mol). This indicates higher corrosion resistance of this alloy in VVER-1000 reactors.