Реалізація першого етапу модернізації однорядних контейнерних збірок зі зразками-свідками металу корпусу реактора ВВЕР-1000 енергоблока № 1 Південноукраїнської АЕС

• Дата: 2022
• Автори: Grytsenko, O., Bukanov, V., Diemokhin, V., Pugach, O., Vasylieva, O., Revka, V., Chyrko, L., Trygubenko, O., Chaikovskyi, Yu.
• Формат: Стаття
• Мова: Ukrainian
• Опубліковано: State Scientific and Technical Center for Nuclear and Radiation Safety 2022
• Онлайн доступ: https://nuclear-journal.com/index.php/journal/article/view/950
• Назва журналу: Nuclear and Radiation Safety

A mandatory condition for the operation of the VVER-1000 reactor is to monitor pressure vessel metal state throughout its lifetime. The regular surveillance specimens program allows monitoring pressure vessel state only during the design lifetime. Therefore, in order to provide materials research support for pressure vessel operation within lifetime extension, modernization programs for single-row container assemblies with surveillance specimens of reactor pressure vessel metal from Ukrainian VVER-1000 NPPs have been developed. The idea of the modernization is to transfer the containers with surveillance specimens to the lower row level of the regular two-row assembly with a rotation by 180º. This provides approximately 2.5 times advanced irradiation of the surveillance specimens in comparison with pressure vessel's level and equalizing fast neutron fluences between the specimens in order to select representative groups for testing. The first stage of the modernization program for single-row container assemblies of SUNPP-1 reactor envisages modernization of the 5L2 assembly with specimens of weld metal No. 3. It was unloaded after the 28th fuel campaign, modernized and returned to the reactor after the 29th campaign. In addition, three metrological assemblies with an extended set of neutron flux indicators were loaded into the reactor as a part of the dosimetric experiment to study neutron field characteristics at the locations of surveillance specimens of the regular program. After the end of the 35th fuel campaign, the modernized 5L2 assembly was unloaded from the reactor and sent to the Institute for Nuclear Research of the National Academy of Sciences of Ukraine, where it was disassembled and fast neutron fluences accumulated by each specimen were determined. In addition, based particularly on the data of the dosimetric experiment, fluence determination uncertainties were evaluated. After irradiation of the modernized container assembly, 12 regular Charpy specimens with close fluences that significantly exceed the fluence on pressure vessel were obtained. This, in turn, allowed us to test it for impact bending in compliance with all regulatory requirements and to perform a reliable evaluation of the critical temperature shift of the brittleness for weld metal No. 3 of the SUNPP-1 reactor pressure vessel for lifetime extension period.