Розрахунковий аналіз елементів ПС СУЗ ВВЕР-1000 з метою обґрунтування продовження строку їх експлуатації

• Дата: 2024
• Автори: Makarenko, А., Chaikovskyi, M., Mazurok, O., Zuyok, V., Mykhaylenko, O.
• Формат: Стаття
• Мова: English
• Опубліковано: State Scientific and Technical Center for Nuclear and Radiation Safety 2024
• Онлайн доступ: https://nuclear-journal.com/index.php/journal/article/view/1135
• Назва журналу: Nuclear and Radiation Safety

This paper presents the main results of strength calculations to justify the integrity of structural elements of the control rods and rod cluster control assemblies under static and dynamic loads in various (all possible) operating modes of rod cluster control assemblies, with the mechanical properties of the material after neutron irradiation, in order to lifetime extend their lifetime. The presented results of calculations of the stress-strain state of rod cluster control assembly elements indicate that the strength conditions are met under the operating modes considered in this paper (including the maximum design basis earthquake). The maximum stresses occur in the joint zone of the cladding with the upper end element, and the corresponding minimum value of the strength factor  is 1.04. The obtained stress values in the control rods and the rod cluster control assembly spider do not exceed the yield strength of the material (RT0.2 = 245 MPa and RT0.2 = 167 MPa, respectively), which does not result in residual deformations. The results of the cyclic strength calculation show that the requirements for cyclic strength are met, the maximum predicted damage is only 5.82 × 10-02 for the control rods and 4.27 × 10-07 for the spider. Consequently, this guarantees the structural integrity of the control rods and rod cluster control assemblies at their extended lifetime. The safe operation (lifetime) of the rod cluster control assemblies currently loaded in VVER‑1000 reactors at Ukrainian NPPs was extended basing on the above justifications and positive results of strength calculations, assuming that fast neutron fluence (E > 0.1 MeV) does not exceed 3.4 × 1022 n/cm2, which, according to the previously performed neutron calculations, corresponds to the lifetime in the manual and automatic control groups up to 38,000 effective hours, in reactor scram groups – approximately up to 113,500 effective hours.